| rash(adjective, careless, foolish, stupid, thoughtless) |
| retarded |
| ridiculous |
| simple-minded |
| slow on uptake(expression, adjective, idiom, dull, insensitive) |
| tenebrous(adjective, obscure, difficult, uncertain, unclear) |
| unaffected(adjective, unresponsive, oblivious, unmoved, impervious) |
| uncertain(adjective, obscure, difficult, unclear, equivocal) |
| unclear(adjective, obscure, difficult, uncertain, equivocal) |
| unfathomable(adjective, obscure, difficult, uncertain, unclear) |
| unfussy(adjective, casual, random, haphazard, indiscriminating) |
| unimpressionable(adjective, hard, impassive, insensitive, unsusceptible) |
| unintelligent(adjective, dull, insensitive, stolid, simple-minded) |
| unintelligible(adjective, obscure, difficult, uncertain, unclear) |
| unkind(adjective, hard, indifferent, unresponsive, insensitive) |
| unmoved(adjective, unresponsive, oblivious, impervious) |
| unsagacious(adjective, careless, foolish, stupid, thoughtless) |
| unsympathetic |
| unwary(adjective, careless, foolish, stupid, thoughtless) |
| vague(adjective, obscure, difficult, uncertain, unclear) |