Meaning of “foolish” - Learner’s Dictionary

foolish

adjective uk us /ˈfuːlɪʃ/

B2 silly and not wise:

a foolish man/mistake
[ + to do sth ] It would be foolish to ignore his advice.
foolishly adverb
foolishness noun [ U ]

(Definition of “foolish” from the Cambridge Learner’s Dictionary © Cambridge University Press)