WordWeb Online

1. Devoid of good sense or judgment
   "foolish remarks"; "a foolish decision";
   - daft [Brit, informal], dumb, stupid, imbecilic, imbecile
    
2. Having or revealing stupidity
   "ridiculous foolish behaviour";
   - anserine, dopy, dopey, goosey, goosy, gooselike, jerky

See also: absurd, cockeyed [informal], derisory, fond, goofy [informal], harebrained, idiotic, ill-advised, ill-conceived, impolitic, imprudent, inadvisable, insane, laughable, ludicrous, mad, mindless, misbegotten, misguided, nonsensical, preposterous, rattlebrained, rattlepated, ridic [informal], ridiculous, scatterbrained, scatty [Brit, informal], silly, stupid, unadvisable, unadvised, unwise, vacant, vacuous, wacky, whacky, zany

Antonym: wise

Encyclopedia: Foolish