Improvisatory refers to an action or performance that is done on the spot without preparation or planning. The antonyms of this word, on the other hand, are words that connote preparedness, planning, and organization. Some of these antonyms include prepared, rehearsed, planned, organized, calculated, intentional, and premeditated. These are words used to describe actions taken with forethought and premeditation, rather than quick, spur-of-the-moment decisions. For instance, a play that is rehearsed for weeks before its performance is not improvisatory, while a speech that is made without any notes or prior planning could be viewed as an improvisatory act.