Italian popular comedy, developed chiefly during the 16th–18th centuries, in which masked entertainers improvised from a plot outline based on themes associated with stock characters and situations.
com·me·dia dell'ar·te (kə-mā'dē-ə děl-är'tē, -tě, -měd'ē-ə) n. A type of comedy developed in Italy in the 16th and 17th centuries and characterized by improvisation from a standard plot outline and the use of stock characters, often in traditional masks and costumes.
[Italian : commedia, comedy + dell'arte, of the guild, professional (from arte, art, craft, guild).]