ADC Theatre Lexicon Long list of definitions for many theatre terms.
Amateur Dramatics Very comprehensive glossary of stagecraft and technical terms for the theatre.
Axiompc Brief theatre glossary.
BC Education Small glossary of theatre terms.
David's Glossary of Theatre Terms Very comprehensive glossary of theatre terms.
East Los Angeles College Theatrepedia Useful glossary of mostly theatre genres and styles.
ImprovComedy Excellent glossary of improv terms.
Lewis Heniford Useful glossary of various theatre genres.
Lutron Small, but useful collection of technical theatre terms.
McGraw-Hill Useful glossary of theatre terms used in Edwin Wilson's text The Theatre Experience.
NWAtalent.com Reasonable glossary of brief definitions to key theatre terms.
Oregon Public Education Network Small glossary of theatre terms.
Playwriting 101 Useful list of playwriting terms and definitions.
Queen's Theatre Hornchurch Comprehensive glossary of theatre terms.
Stage Specs Glossary of technical terms for the theatre.
Theatrecrafts Excellent glossary of technical terms for the theatre, searchable by letter, word or category.
Thomson Gale Useful glossary of literary terms (many of these common theatre terms/genres etc).
Tidelanders Barbershop Chorus Extensive glossary of theatre terms.
Tupelo Community Theatre Archived version of a useful, but less comprehensive glossary of theatre terms.
Vincent Lighting Systems Comprehensive glossary of stage lighting terms.
Weber State University Dictionary of theatrical terms.