| halfwitted |
| ignorant(adjective, simple, slow, silly, foolish) |
| nuts(adjective, stupid, crazy, insane) |
| risible |
| thickheaded(adjective, slow, stupid) |
| balmy(adjective, knowledge, slang, ability, stupid) |
| cockeyed(adjective, knowledge, ability, informal, impractical) |
| blockheaded(adjective, slow, foolish, stupid, impulsive) |
| childish |
| crackpot(adjective, foolish, impractical, half-baked, doomed) |
| gormless |
| hare-brained |
| illogical(adjective, silly, stupid, insignificant, unreasonable) |
| irresponsible(adjective, foolish, stupid, impractical, half-baked) |
| jerky(adjective, weak, simple, knowledge, slang) |
| pointless(adjective, dull, simple, slow, silly) |
| simpleminded(adjective, dull, simple, silly, foolish) |
| stolid(adjective, dull, simple, slow, foolish) |
| thick-witted(adjective, foolish, stupid, crazy, insane) |
| blithering(adjective, foolish) |