| incomprehensible |
| irresponsible(adjective, silly, foolish, stupid, fantastic) |
| loopy(adjective, knowledge, ability, informal, foolish) |
| delirious(adjective, crazy, mad, odd, insane) |
| dim-witted(adjective, foolish) |
| doltish(adjective, dull, weak, simple, silly) |
| droll |
| eccentric(adjective, silly, foolish, fantastic, ridiculous) |
| empty(adjective, simple, value, stupid, insignificant) |
| fallacious(adjective, foolish, unreasonable, absurd, irrational) |
| fantastical(adjective, crazy, mad, odd, insane) |
| feeble-minded(impractical, half-baked, doomed) |
| fool |
| foolhardy(adjective, silly, foolish, stupid, fantastic) |
| futile(adjective, dull, simple, value, foolish) |
| half-baked(dull, simple, silly, foolish, stupid) |
| harebrained(adjective, weak, simple, knowledge, ability) |
| hollow(adjective, value, insignificant, unimportant, empty) |
| ignorant(adjective, foolish, stupid, absurd, impractical) |
| implausible(adjective, strange, crazy, insane, absurd) |