| off top of head(expression, adjective, idiom, simple, natural) |
| offhand(adjective, simple, natural, casual, impulsive) |
| simple(adjective, natural, casual, impulsive, willing) |
| spontaneous(adjective, impulsive, willing, unforced, unprompted) |
| unartful(adjective, simple, natural, casual, impulsive) |
| unavoidable(adjective, simple, natural, casual, impulsive) |
| unbidden(adjective, simple, natural, casual, impulsive) |
| uncompelled(adjective, simple, natural, casual, impulsive) |
| unconscious(adjective, simple, natural, casual, impulsive) |
| unconstrained(adjective, simple, natural, casual, impulsive) |
| uncontrived(adjective, simple, natural, casual, impulsive) |
| uncontrolled(adjective, simple, natural, casual, impulsive) |
| unforced(adjective, simple, natural, casual, impulsive) |
| unintentional(adjective, simple, natural, casual, impulsive) |
| unplanned(adjective, simple, natural, casual, impulsive) |
| unprompted(adjective, simple, natural, casual, impulsive) |
| unsophisticated(adjective, simple, natural, casual, impulsive) |
| unstudied(adjective, simple, natural, casual, impulsive) |
| up front(expression, adjective, simple, natural, casual) |
| voluntary(adjective, simple, natural, casual, impulsive) |