verb

1. To make something up or invent it as one goes on; to proceed guided only by imagination, instinct, and guesswork rather than by a careful plan.

   “He had no speech prepared, so he improvised.”

Synonyms: fly by the seat of one's pants, play by ear, punt, think on one's feet, wing it

adjective

1. Created by improvisation; impromptu; unrehearsed.