| fatuous(adjective, silly, foolish, stupid, crazy) |
| flighty(adjective, ability, vague, unreliable, changeable) |
| goofy(adjective, impractical, frivolous, half-baked, doomed) |
| silly(adjective, ability, foolish, stupid, crazy) |
| featherbrained(adjective, ability) |
| frivolous(adjective, ability) |
| frothy(adjective, ability) |
| harebrained(adjective, ability, foolish, crazy, vague) |
| witless(adjective, silly, foolish, innocent, vague) |
| dim-witted |
| empty-headed(adjective, ability) |
| half-baked(adjective, foolish, stupid, impulsive, unintelligent) |
| airheaded(adjective, stupid, unstable, unreliable, changeable) |
| boneheaded(silly, impulsive, impractical, unintelligent, unaware) |
| brainless(silly, foolish, impulsive, impractical, unintelligent) |
| bubbleheaded(adjective, unstable, unreliable, changeable, fickle) |
| dense(adjective, dull, innocent, unfamiliar, unconscious) |
| dizzy(adjective, slang, ability) |
| dull(simple, silly, foolish, stupid, crazy) |
| dumb(foolish, stupid, crazy, insane, unintelligent) |