| impromptu(adjective, adverb, free, spontaneous, unprepared) |
| ad lib(expression, adjective, free, informal, mock) |
| extemporaneous(adjective, free, casual, spontaneous, unprepared) |
| offhand(adjective, free, informal, casual, spontaneous) |
| by ear(expression, adjective, free, fake, informal) |
| extempore(adjective, free, casual, impulsive, spontaneous) |
| improv(adjective, free, fake, informal, mock) |
| improvisatory(adjective, free, fake, informal, casual) |
| improvised(adjective, free, spontaneous, unprepared, impromptu) |
| makeshift(adjective, free, informal, casual, spontaneous) |
| on-the-spot(adjective, free, fake, informal, casual) |
| on impulse(expression, adjective, free, fake, informal) |
| spontaneous(adjective, free, casual, unprepared, unplanned) |
| spur-of-the-moment(adjective, free, spontaneous, unprepared, unplanned) |
| tossed off(expression, adjective, free, informal, mock) |
| unpremeditated(adjective, free, casual, spontaneous, unprepared) |
| unprepared(adjective, free, spontaneous, impromptu, unplanned) |
| unstudied(adjective, free, informal, casual, spontaneous) |
| ad-lib(adjective, spontaneous, unprepared, impromptu, unplanned) |
| ad hoc(expression, adjective, free, casual, unrehearsed) |