| off top of head(expression, adjective, idiom, simple, natural) |
| offhand(adjective, simple, natural, casual, impulsive) |
| outgoing(adjective, artless) |
| overt(adjective, artless) |
| plain-spoken(adjective, artless) |
| simple(adjective, honest, plain, natural, casual) |
| spontaneous(adjective, impulsive, willing, unforced, unprompted) |
| un-artificial(adjective, artless) |
| unavoidable(adjective, simple, natural, casual, impulsive) |
| unbeguiling(adjective, artless) |
| unbidden(adjective, simple, natural, casual, impulsive) |
| uncalculating(adjective, artless) |
| 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) |
| undeceitful(adjective, artless) |
| undeceiving(adjective, artless) |
| undeceptive(adjective, artless) |