| impromptu(adjective, adverb, informal, unprepared, unplanned) |
| improvised(adjective, informal, spontaneous, unplanned, unrehearsed) |
| ad lib(expression, adjective, idiom, spontaneous, unprepared) |
| extemporaneous(adjective, fake, informal, spontaneous, unrehearsed) |
| unplanned(adjective, informal, spontaneous, unprepared, unrehearsed) |
| unpremeditated(adjective, spontaneous, unprepared, unplanned, unrehearsed) |
| unprepared(adjective, informal, spontaneous, unplanned, unrehearsed) |
| unstudied(adjective, spontaneous, unprepared, unplanned, unrehearsed) |
| extempore(adjective, informal, spontaneous, unprepared, unrehearsed) |
| makeshift(adjective, informal, spontaneous, unplanned, unpremeditated) |
| ad-lib(adjective, fake, informal, spontaneous, unprepared) |
| off the cuff(expression, adjective, idiom, unprepared, unplanned) |
| offhand(adjective, spontaneous, unprepared, unplanned, unrehearsed) |
| snap |
| spontaneous(adjective, informal, unprepared, unplanned, unrehearsed) |
| unarranged(spontaneous, unprepared, unplanned, unrehearsed, unpremeditated) |
| unrehearsed(adjective, informal, spontaneous, unprepared, unplanned) |
| according to pleasure(expression, adjective, informal, unplanned, extemporize) |
| ad-libed |
| ad hoc(expression, idiom, informal, spontaneous, unprepared) |