| abrupt(adjective, impulsive) |
| ad hoc(expression, adjective, idiom, free, casual) |
| ad libitum(expression, adjective, idiom, adverb, informal) |
| extemporized(adjective, informal, spontaneous, unprepared, unplanned) |
| ill-considered(adjective, impulsive, unqualified, unsuspecting, unready) |
| improv(adjective, adverb, free, spontaneous, unprepared) |
| improviso(adjective, free, casual, spontaneous, unprepared) |
| instinctive(adjective, impulsive, unprompted, spur-of-the-moment) |
| natural(adjective, impulsive, unprompted, spur-of-the-moment) |
| snap(adjective, free, informal, casual, impulsive) |
| according to pleasure(expression, informal, impulsive, unplanned, extemporaneous) |
| as one thinks best(expression, informal, impulsive, unplanned, extemporaneous) |
| as one wishes(expression, adjective, adverb, informal, impulsive) |
| at first glance(expression, idiom, free, informal, snap) |
| at will(expression, adjective, adverb, informal, impulsive) |
| automatic(adjective, free, casual, impulsive, spontaneous) |
| autoschediastic(free, casual, impulsive, spontaneous, unprepared) |
| by ear(expression, free, casual, offhand, impromptu) |
| candid |
| casual(adjective, free, impulsive, spontaneous, unprepared) |