foolish

Synonyms: absurd asinine brainless cockamamy crazy daffy daft dippy doltish dotty fantastic fatuous feebleminded half-baked half-witted harebrained ill-advised ill-considered imbecilic imprudent incautious indiscreet injudicious insane irrational jerky kooky loony ludicrous lunatic mad moronic nerdy nutty preposterous ridiculous senseless short-sighted silly simple stupid unintelligent unreasonable unwise wacky weak witless zany

Antonyms: careful cautious circumspect prudent sensible serious thoughtful unfoolish wise