Lazzi (from the Italianlazzo, a joke or witticism) is a bit of well-rehearsed comic action used in the Commedia dell'arte. Most English-speaking troupes use the Italian plural "lazzi" as the singular and "lazzis" for the plural.
During improvised performances a lazzi may be used to fill time or to ensure a certain frequency of laughs in a show. For practical purposes a lazzi may be any bit of business that may be easily recalled and performed in another situation.