Synonyms for Foolish:

adj.

absurd (adjective)
absurd, anachronistic, bizarre, contradictory, crazy, eccentric, fallacious, farcical, idiotic, illogical, implausible, impossible, inane, incongruous, inconsistent, invalid, irrational, laughable, loony, ludicrous, meaningless, nonsensical, outlandish, paradoxical, preposterous, ridiculous, self-contradictory, senseless, silly.
daft (adjective)
witless.
foolish (adjective)
asinine, blithering, blockheaded, brainless, cretinous, dim-witted, doltish, dopey, dotty, dumb, goofy, half-witted, ignorant, imbecilic, loony, moronic, nitwit, crackpot, bone-headed, chuckle-headed, knuckle-headed, lame-brained, meat-headed, absurd, crazy, idiotic, inane, nonsensical.
harebrained (adjective)
rattlebrained.
ignorant (adjective)
empty-headed, illiterate, mindless, simple, uneducated, uninformed, unintelligent, unlearned, brainless, ignorant.
insane (adjective)
balmy.
nonsensical, idiotic (adjective)
absurd, asinine, brainless, cockamamy, crazy, doltish, dotty, fatuous, half-witted, harebrained, imbecilic, insane, irrational, loony, ludicrous, lunatic, mad, moronic, preposterous, ridiculous, senseless, silly, simple, unintelligent, unreasonable, unwise, wacky, witless, zany, dippy.
ridiculous (adjective)
comical, curious, dubious, grotesque, incredible, laughable, oddball, outrageous, poppycock, weird, absurd, bizarre, crazy, eccentric, farcical, ludicrous, nonsensical, outlandish, preposterous, ridiculous, silly.
senseless (adjective)
asinine.
shallow (adjective)
shallow.
simple (adjective)
softheaded.
unintellectual (adjective)
defective, half-wit, unintellectual, cretinous, idiotic, imbecilic, moronic, unintelligent.
zany (adjective)
zany.

n.

abashed, ashamed, contrite, embarrassed, guilty, repentant, sorry, uncomfortable, feel/look small. ability, hasty, impetuous, impulsive, insensate, irresponsible, planned, shallow, undiscriminating, unthinking, witless, Weak-minded. balmy, cockeyed, knowledge, loopy, lunatic, softheaded, tomfool, unearthly, dippy. foolish (noun)
absurd, anserine, asinine, cockamamie, cockamamy, derisory, dopey, dopy, fatuous, fond, fool, goofy, gooselike, goosey, goosy, harebrained, ill-conceived, inane, insane, laughable, ludicrous, mad, mindless, misguided, nonsensical, preposterous, rattlebrained, rattlepated, ridiculous, sappy, scatterbrained, scatty, silly, unreasonable, unwise, vacuous, wacky, whacky, zany.
silly (noun)
study at absurd.

Other synonyms:

abashed, ashamed, contrite, embarrassed, guilty, loopy, repentant, softheaded, sorry, uncomfortable, undiscriminating, unthinking, witless, dippy. cockeyed, impetuous, impulsive, irresponsible, shallow, Weak-minded. lunatic. unearthly. crazy
balmy.
stupid
insensate.
Other relevant words:
abashed, ability, absurd, anserine, ashamed, balmy, cockamamie, cockamamy, cockeyed, contrite, derisory, dopy, embarrassed, fatuous, fond, fool, gooselike, goosey, goosy, guilty, harebrained, hasty, ill-conceived, impetuous, impulsive, insane, insensate, irresponsible, knowledge, loopy, lunatic, mad, misguided, planned, rattlebrained, rattlepated, repentant, sappy, scatterbrained, scatty, shallow, softheaded, sorry, tomfool, uncomfortable, undiscriminating, unearthly, unreasonable, unthinking, unwise, vacuous, wacky, whacky, witless, zany, Weak-minded, dippy.

Usage examples for foolish

  1. He is not the sort of man to do foolish things, and that is foolish on the face of it. – The Grell Mystery by Frank Froest
  2. John, don't be foolish – John Halifax, Gentleman by Dinah Maria Mulock Craik
  3. Oh, you foolish boy! – The Awakening of Helena Richie by Margaret Deland