| ad lib(expression, adjective, free, informal, casual) |
| impromptu(adjective, adverb, free, casual, offhand) |
| improv(adjective, adverb, free, fake, informal) |
| improvisatory(adjective, free, fake, informal, casual) |
| improviso(adjective, free, fake, informal, casual) |
| makeshift(adjective, adverb, free, casual, impromptu) |
| off the top of head(expression, idiom, free, informal, casual) |
| offhand(adjective, adverb, free, casual, impromptu) |
| on-the-spot(adjective, free, fake, informal, casual) |
| on impulse(expression, adjective, free, fake, informal) |
| ad-lib(adjective, adverb, free, fake, casual) |
| ad hoc(expression, adjective, free, casual, unrehearsed) |
| at first glance(expression, idiom, free, informal, casual) |
| automatic(adjective, free, informal, casual, impulsive) |
| autoschediastic(adjective, free, fake, casual, impulsive) |
| casual(adjective, free, informal, impulsive, unprepared) |
| expedient(adjective, free, informal, casual, snap) |
| extemporaneous(adjective, free, casual, impulsive, spontaneous) |
| extemporary(adjective, free, fake, casual, impulsive) |
| extempore(adjective, free, casual, impulsive, unprepared) |