AGITPROP
The original sense of agitprop was "agitation and propaganda on behalf of Communism", or "a government agency or department responsible for agitation and propaganda". The main current sense of the word is simply "propaganda, especially socially or politically motivated propaganda appearing in literary works, films, etc."; though the word often refers to political propaganda, it is not restricted to communist doctrine.
The word agitprop is first found in English sources in the mid 1930s.
From the Random House Word of the Day website.

BALLAD OPERA
A theatrical entertainment popular in early 18th-century England, taking the form of a satirical play interspersed with traditional or operatic songs. The best-known example is John Gay's The Beggar's Opera (1728).
[Definition from Oxford Languages, via Google]

BOURGEOIS TRAGEDY
Bourgeois tragedy (German: Bürgerliches Trauerspiel) is a form of tragedy that developed in 18th-century Europe. It is a fruit of the enlightenment and the emergence of the bourgeois class and its ideals. It is characterized by the fact that its protagonists are ordinary citizens.
Wikipedia entry

BRECHT / BRECHTIAN*
TO BE DEFINED

BURLESQUE
Adult-orientated entertainment, consisting of dancing, minimal costumes, songs and comic sketches. Popular from the 1840s in Europe and the USA.

COMEDY
An entertaining performance designed to make an audience laugh. 
In Greek and Roman theatre, any play with a happy ending was called a comedy, regardless of whether it was funny. 
Sketch Comedy - a series of short unconnected scenes, with comedic and/or stylised performances, containing jokes, which may be topical and/or satirical.  
High Comedy (also known as pure or highbrow comedy) is a type of comedy characterized by witty dialogue, satire, biting humor, or criticism of life.
Low Comedy (also known as lowbrow humour) is more physical comedy, using slapstick or farce, with no purpose other than to cause the audience to laugh. 
See also SATIRE.

DINNER THEATRE
A theatre performance that includes a meal, either at the same venue or at an adjacent restaurant. 
Although it was popular in the 1950s in the USA (as Dinner Theater), there are still many venues worldwide where a live performance is accompanied by a meal, usually in a tourist-focussed themed attraction. Examples run daily in Las Vegas or Orlando, Florida, and include murder-mystery themes, medieval themes, or magic shows with dinner served. 

DOCUMENTARY THEATRE
Documentary theatre, or theatre of fact, is theatre that wholly or in part uses pre-existing documentary material (such as newspapers, government reports, interviews, etc.) as source material for the script, ideally without altering its wording.
Where it's featured solely on the words of others, usually members of the public in a particular situation, it's known as VERBATIM THEATRE.

DUMBSHOW
A piece of mimed action. Used in Shakespeare's Hamlet to summarise and comment on the main plot. 

END ON
Traditional audience seating layout where the audience is looking at the stage from the same direction. This seating layout is that of a Proscenium Arch theatre.
Also known as Proscenium Staging.
The end-on stage can be split into 9 areas: upstage right, upstage centre, upstage left, centre stage right, centre stage, centre stage left, downstage right, downstage centre, downstage left.
See also THRUST, IN THE ROUND, TRAVERSE.

EPIC THEATRE
Epic theatre is a theatrical movement arising in the early to mid-20th century from the theories and practice of a number of theatre practitioners who responded to the political climate of the time through the creation of a new political theatre.
Epic theatre is not meant to refer to the scale or the scope of the work, but rather to the form that it takes^. Epic theatre emphasizes the audience's perspective and reaction to the piece through a variety of techniques that deliberately cause them to individually engage in a different way The purpose of epic theatre is not to encourage an audience to suspend their disbelief, but rather to force them to see their world as it is. (from Wikipedia)
Wikipedia entry

EXPRESSIONISM
Theatre design and performance style which places greater value on emotion than realism. The trademark Expressionist effects were often achieved through distortion.

FARCE
Form of comedy play originated in France, using fast-paced physical action and visual comedy more than humour based on language.
In London's West End, following the Second World War, there were farces at the Aldwych Theatre (the Aldwych Farces, particularly those by Ben Travers) and at the Whitehall Theatre (the Whitehall Farces). 

FORUM THEATRE
Forum theatre is a type of theatre created by the influential practitioner Augusto Boal as part of what he calls his "Theatre of the Oppressed." While practicing earlier in his career, Boal would apply simultaneous dramaturgy. In this process the actors or audience members could stop a performance, often a short scene in which a character was being oppressed in some way. The audience would suggest different actions for the actors to carry out on-stage in an attempt to change the outcome of what they were seeing. This was an attempt to undo the traditional actor/audience divide and to bring audience members into the performance, to have an input into the dramatic action they were watching.

FUTURISM
An artistic and social movement that started in Italy in the early 20th century. In art, it celebrated technologies of the time - air travel, machinery, industrialisation. Futurist ideas helped to form Art Deco, Vorticism, Constructivism, Surrealism, Dada, and much later Neo-Futurism. In theatre, it fought against classical forms of theatre and celebrated the youthful, spontaneous, and satirical, encouraging vaudeville and music hall forms. 
Wikipedia entry

GRAND GUIGNOL
Shock theatre form originally from Le Grand Guignol theatre in Montmartre, Paris (opened in 1897). Specialised in portraying the macabre & gruesome to the delight and horror of the audience.

IMMERSIVE THEATRE
1) A piece of linear performance where the venue has been adapted / altered to make it part of the narrative of the story. Secret Cinema events are immersive in this sense. 
2) A piece of non-linear performance where a non-theatre venue has been completely transformed into a highly detailed world within which the audience is free to roam and see various parts of the story performed in appropriate locations. The UK company Punchdrunk created the concept of audience members wearing masks which allow them to wander around the space anonymously.
Punchdrunk Theatre

IN THE ROUND
Theatre in the Round is a form of audience seating layout where the acting area is surrounded on all sides by seating. There are often a number of entrances through the seating. Special consideration needs to be given to onstage furniture and scenery as audience sightlines can easily be blocked.
Stage managers and directors often use the idea of a clock face to describe actor positions on stage (e.g. the aisle nearest the technical point is described as the 12 O'clock position, with other aisles described as 3, 6 and 9 O'clock.)
See also ARENA, THRUST, END ON, TRAVERSE.

INSTALLATION
1) An electrical system in a particular building (e.g. "the stage lighting installation was tested last year")
2) A piece of art designed to transform a particular room or building into something other than a room in an art gallery. Installations often use complex audio-visual equipment and can be intensely immersive experiences. (e.g. "In the studio space this week we have an installation by John Doe entitled 'Space'")

LEGITIMATE THEATRE
The term was originally derived from the UK Licencing Act of 1737, which sought to censor and control what theatrical performances were able to say about the government. 
In 1660, after the Restoration of Charles II, the previous ban on public entertainments was lifted, and letters patent were granted to Thomas Killigrew and William Davenant to form two theatre companies to perform 'serious drama'.
Other theatres were not permitted to perform such serious work, but could put on comedy, pantomime or melodrama. 
All performances were licenced by the Examiner of Plays. 
The 1843 Theatres Act permitted all theatres to perform 'serious' drama, but censorship and licencing were in place until 1968, when a new Theatres Act was created. 

Legitimate theater now refers to theatres that produce 'serious', high-quality professional work rather than variety or burlesque. 

MELODRAMA
A Melodrama is a dramatic work that exaggerates plot and/or characters in order to appeal to the emotions. It is usually based around having the same character traits, (for example, a hero, who is fearless and who the audience is rooting for, the heroine, who is usually in peril of some kind, which the hero rescues her from; the villain (usually likes the heroine too) and villain's sidekick (typically gets in the way of or annoys the villain).
The term is also used in scholarly and historical musical contexts to refer to dramas of the 18th and 19th centuries in which orchestral music or song was used to accompany the action.

METATHEATRE
This term, coined by Lionel Abel, has entered into common critical usage; however, there is still much uncertainty over its proper definition and what dramatic techniques might be included in its scope. Abel described metatheatre as reflecting comedy and tragedy, at the same time, where the audience can laugh at the protagonist while feeling empathetic simultaneously.
Wikipedia entry

MIME
Form of performance with no spoken words. Plot, character etc. are conveyed to the audience by movement and gesture. From the Greek Mimos.

See also Physical Theatre.
Marcel Marceau Foundation for the Advancement of the Art of Mime
Mummenschanz

MINIMALISM
Artistic movement starting in the 1960s which aspired to simple form and design. A minimalist theatrical stage design might involve only the essential compoents of the scene (e.g. a single chair and a suspended window frame, and no other set or furniture). 
The ruling mantra is 'Less is More'. It is often best to take away things when the stage picture is not right, rather than adding more - this applies to stage lighting as well as scenic design. 

MORALITY PLAY
An allegorical performance in whcih the protagonist is met by personifications of various moral attributes who try to prompt him to choose a godly life over one of evil. Popular in Europe during the 15th and 16th centuries.
Wikipedia entry

MUMMERS PLAY
A traditional folk play, performed on a makeshift stage in villages aross Britain, performed by amateur actors. 
Wikipedia entry

MUSIC HALL
A type of British theatrical entertainment popular between 1850 and 1960. It involved a mixture of popular song, comedy, speciality acts and variety entertainment. The term is derived from a type of theatre or venue in which such entertainment took place. British music hall was similar to American vaudeville, featuring rousing songs and comic acts, while in the United Kingdom the term vaudeville referred to more working-class types of entertainment that would have been termed burlesque in America.

MUSICAL THEATRE
(From Wikipedia) Musical theatre is a form of theatrical performance that combines songs, spoken dialogue, acting and dance. The story and emotional content of a musical – humor, pathos, love, anger – are communicated through words, music, movement and technical aspects of the entertainment as an integrated whole. Although musical theatre overlaps with other theatrical forms like opera and dance, it may be distinguished by the equal importance given to the music as compared with the dialogue, movement and other elements. 
Concept Musical: a work of musical theatre whose book and score are structured around conveying a theme or message, rather than emphasizing a narrative plot. Examples include Cabaret and Company. 
Jukebox Musical: A stage musical show that has been constructed from pre-released existing songs, usually from one artist or genre.Examples include Bat Out Of Hell, We Will Rock You and Mamma Mia!
Megamusical: Similar to a movie Blockbuster, the Megamusical is spectacular and costly, and is designed to reap financial rewards for its' producers. Examples include Hamilton, Wicked, The Lion King etc. 
Sung-through / Through-Sung / Through-Composed: A musical where the dialogue is completely sung. Examples include Cats, Hamilton etc. 
Abbreviated to MT.

MYSTERY PLAY
Also known as a Miracle Play. Traditional since medieval times, the Mystery Play is a re-enactment of bliblical scenes, usually performed outdoors in a small town or village, by the community. 
A Passion Play is a cycle of plays that portray the Easter story, specifically. One of the most famous is the Oberammergau Passion Play, performed in the German town in years ending in a zero.  
What is a Miracle Play
Oberammergau Passion Play

NATURALISM
1) Lighting Design: A naturalistic approach to lighting design requires lanterns to be placed in ways that duplicate where the light would come from in nature. For example, a sunny day outdoor scene would be lit primarily from above the acting area, with fill lighting in from the sides as if from the cloud. A dark room would be lit by moonlight through a window, and the light level would increase when a door is opened from a lit corridor or when a light fitting is turned on.
2) Performance: A naturalistic performance (following the techniques of Stanislavski) requires that the actor completely understands and inhabits every aspect of the characters' life, as well as the motivation and lines that are to be spoken. 
3) Scenic Design: The set designer aims to reproduce reality as closely as possible.

Heightened Naturalism involves exaggerating the natural elements of the scene for dramatic (or comedic) purposes. 

NOH THEATRE

Wikipedia entry

ONE PERSON SHOW
An entire performance for a single performer. Also known as One-Man Show or One-Woman Show. 
Relies on a strong characterisation and a confident performer. The performer is somes also the writer, but not necessarily. 
"Fleabag" is written and performed by Phoebe Waller-Bridge and was very successful at the Edinburgh Fringe and in London. 
"Old Herbaceous" is a one-man show performed in an on-stage recreation of a gardeners' potting shed. 
There are thousands of other examples. 
See also MONOLOGUE and SOLILOQUY. 
Fleabag
Old Herbaceous

OPERA
1) European terminology meaning Opera House - lavishly decorated proscenium theatre with orchestra pit. See TOSCA.
2) Musical form. Highly dramatic and stylised form where the text is completely sung.
See also OPERETTA, OPERA HOUSE.

OPERETTA
A short (often humourous) opera with songs (sometimes in an operatic style) and some spoken dialogue. 
The most well-known are by Gilbert & Sullivan, some of which were first performed at the Savoy Theatre in London. 

PANTOMIME
1) A pantomime (often shortened to Panto) is a musical-comedy family-orientated theatrical production traditionally performed in United Kingdom, Australia, New Zealand, Canada, Zimbabwe, Jamaica, South Africa, India, Ireland, Gibraltar, and Malta, at Christmas-time. The panto often features slapstick or messy comedy routines, children dancing, recent songs, spectacular sets and colourful costumes, and is often themed around a fairy story or nursery rhymes.
Popular pantos include Cinderella, Aladdin, Jack and the Beanstalk, Mother Goose, Sleeping Beauty, Snow White and the Seven Dwarfs, Dick Whittington and His Cat, Puss in Boots etc.
There are a number of traditions with panto, including that the baddie / villain must enter stage left, and the goodie / fairy godmother must enter stage right. The colour green is often used for the baddie, and pink for the goodie.  
2) Pantomime is an ancient type of performance with no spoken words, often now shortened to 'Mime'. 
Puss in Boots, December 2013, Hackney Empire - Audio Slideshow (The Guardian)

PERFORMANCE ART
An interdisciplinary performance presented to an audience. The performance may be either scripted or unscripted, random or carefully orchestrated; spontaneous or otherwise carefully planned with or without audience participation. The performance can be live or via media; the performer can be present or absent. It can be any situation that involves four basic elements: time, space, the performer's body, or presence in a medium, and a relationship between performer and audience. Performance art can happen anywhere, in any venue or setting and for any length of time. The actions of an individual or a group at a particular place and in a particular time constitute the work.

PHYSICAL THEATRE
Physical theatre is a genre of performance which makes use of the body (as opposed to the spoken word) as the primary means of performance and communication with an audience. In using the body, the performer or actor will concentrate on:
The use of body shape and position
Facial expressions
Rhythmical movement, pace and the energy of the body
Gesture
Posture
Gait
Physical theatre can be distinquished from dance in that it tends to focus more on narrative, character and action. However, the boundaries between the two are rather blurred.
There are various styles and genre of physical theatre. These include:
Physical comedy - where the body is the primary means of comic creation
Mime
Stomp- where the body, with external objects, is used for its percussive potential
Some forms of puppetry
Circus
The most famous institution devoted to physical theatre is the Lecoq school in Paris. Students here follow the method of Jacques Lecoq, which developed out of his experience of mask work, commedia dell'Arte and his interest in the physicality of performance.
Definition from Wikipedia - click for more
Lecoq School

PROMENADE
Form of staging where the audience moves around the performance space and sees the play at a variety of different locations. See also IMMERSIVE THEATRE.

REVUE
A type of performance consisting of lighthearted songs and comic sketches - a variety show.

SINAKULO
A retelling of the story of Jesus Christ, performed each year during Holy Week in lowland Philippines. Performed outdoors by and for the community in villages that observe this folk drama tradition.
See also MYSTERY PLAYS.

SITCOM
Short for Situation Comedy - a Radio or TV show featuring a regular cast of characters who, each episode, find themselves in a different situation, with comic outcomes. There are often storylines or character arcs which continue alongside the weekly situations. Examples are Friends, The Office, Will & Grace, Blackadder, Futurama, Fawlty Towers etc.

SITE-SPECIFIC THEATRE
A piece of performance which has been designed to work only in a particular non-theatre space. The space may have been adapted to fit into the themes or style of the production. A site-sensitive (or space-sensitive) piece, on the other hand, will not adapt the space, but work with it's style and history to create a piece of performance. See also PROMENADE, IMMERSIVE THEATRE, INSTALLATION.

SKIT
A short (usually) comedic sketch, often satirical or a parody.

SONGSHEET
Traditional ending to a British Pantomime performance, usually involving the Dame character encouraging the audience to sing along with a traditional (and/or silly) song that conveniently allows the stage management team to set up the WALKDOWN, a usually spectacular finale to the performance. The lyrics of the song are flown in, in front of the frontcloth. This sequence may also involve announcing any special visitors or audience birthdays, and possibly inviting a couple of children to the stage to take part in the song. 

SPECTACLE
A theatrical performance using large scale scenery and effects to wow the audience. Popularised in Victorian times, they featured water tanks, live animals, moving stages and aerial effects.

STASIMON
(Greek Tragedy) A stationary song, composed of strophes and antistrophes and performed by the chorus in the orchestra, which ends each Episode.
Wikipedia entry

SUMMER STOCK
(USA) American term for a theater or organisation that produces work only during the summer, often as part of a festival working with young actors at the start of their career, working as a repertory company, using and adapting existing costumes, props and scenic items. Summer Stock companies operate outside large cities, especially those where commercial theatre is part of the ecosystem. 

THEATRE OF CRUELTY
Theatre of Cruelty is a form of theatre originally developed by avant-garde French playwright, essayist, and theorist Henry Becque.
Antonin Artaud, some 50 years later, is also seen as a main contributor to the genre, notably with The Theatre and its Double. Originally a member of the surrealist movement, Artaud eventually began to develop his own theatrical theories. The Theatre of Cruelty can be seen as a break from traditional Western theatre and a means by which artists assault the senses of the audience, and allow them to feel the unexpressed emotions of the subconscious. While Artaud was only able to produce one play in his lifetime that reflected the tenets of the Theatre of Cruelty, the works of many theatre artists reflect his theories. These artists include Jean Genet, Jerzy Grotowski, and Peter Brook. (from Wikipedia)
Wikipedia entry

THEATRE OF THE ABSURD
The Theatre of the Absurd is a post–World War II designation for particular plays of absurdist fiction written by a number of primarily European playwrights in the late 1950s. It is also a term for the style of theatre the plays represent. The plays focus largely on ideas of existentialism and express what happens when human existence lacks meaning or purpose and communication breaks down. The structure of the plays is typically a round shape, with the finishing point the same as the starting point. Logical construction and argument give way to irrational and illogical speech and to the ultimate conclusion—silence.
Examples of absurdist plays include Beckett's Waiting for Godot, Jean Genet's The Maids and Stoppard's Rosencrantz and Guildenstern Are Dead. 
Wikipedia entry

TRAGEDY
Tragedy (from the Greek tragos which means 'goat' and oide which means 'song') is a form of drama based on human suffering that invokes in its audience an accompanying catharsis or pleasure in the viewing. While many cultures have developed forms that provoke this paradoxical response, the term tragedy often refers to a specific tradition of drama that has played a unique and important role historically in the self-definition of Western civilization.

TRAGI-COMEDY / TRAGICOMEDY
Tragicomedy is a literary genre that blends aspects of both tragic and comic forms. Most often seen in dramatic literature, the term can variously describe either a tragic play which contains enough comic elements to lighten the overall mood or a serious play with a happy ending.

TRAVERSE
Form of staging where the audience is on either side of the acting area.
Also known as ALLEY or AVENUE staging. 
See also IN THE ROUND, END ON, THRUST.

USITT
United States Institute of Theatre Technology.
Founded in 1960. Publisher of Theatre Design and Technology and Sightlines journals, which are available online (see Publications in the Theatrecrafts.com Archive section).
USITT Website

VAUDEVILLE
A type of light-hearted entertainment popular chiefly in the US in the early 20th century, featuring a mixture of speciality acts such as burlesque comedy and song and dance.

VECCHIO
Category of stock character from Commedia dell'Arte - consists of the 'old man' characters: Il Dottore (the Doctor), Pantalone, Il Capitano (the Captain). Vecchio is the Italian word for 'old'. 

ZARZUELA
A Spanish lyric-dramatic genre that alternates between spoken and sung scenes, the latter incorporating operatic and popular song, as well as dance.