To improvise; to extemporize.

unpremeditated; impromptu

Able to be improvised.

A form of improvisational theatre performed with little predetermination of subject matter and structure, but with interaction with the audience. / An instance of such theatre.

a form of theatre in which the actors perform spontaneously, without a script

plural of improvisational comedy

An unconventional or amateur explosive weapon made from nonmilitary components, especially one used by guerillas, commandos or terrorists.

plural of improvised explosive device