| spontaneous(noun, adjective, free, fake, informal) |
| unpremeditated(noun, adjective, free, chance, casual) |
| accidental(adjective, careless, chance, casual, planned) |
| casual(adjective, free, simple, fake, natural) |
| unintentional(adjective, simple, natural, chance, casual) |
| chance(adjective, careless, casual, planned, erratic) |
| fortuitous(adjective, chance, casual, planned, erratic) |
| random(adjective, insignificant, chance, casual, irregular) |
| impromptu(adjective, free, simple, fake, informal) |
| unexpected(adjective, adverb, chance, impulsive, planned) |
| unintended(adjective, chance, planned, unknowing, unintentional) |
| haphazard(adjective, insignificant, chance, casual, irregular) |
| unwitting(adjective, careless, casual, planned, reckless) |
| inadvertent(adjective, planned, unknowing, unaware, unintentional) |
| hasty(adjective, impulsive, rash, unthinking) |
| unprepared(adjective, free, ready, casual, unqualified) |
| adventitious(adjective, chance, planned, haphazard, unintentional) |
| extemporaneous(noun, adjective, simple, informal, natural) |
| offhand(noun, adjective, free, simple, fake) |
| undesigned(adjective, planned, unknowing, unaware, unintentional) |