Definition of stupid adjective from the Oxford Advanced Learner's Dictionary

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stupid

adjective
ˈstjuːpɪd
 
; ˈstuːpɪd
 
 
stupider, stupidest
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more stupid and most stupid are also common
1 showing a lack of thought or good judgement
Synonym
foolish
, silly
a stupid mistakeIt was a pretty stupid thing to do.I was stupid enough to believe him.It was stupid of you to get involved.
2 (disapproving) (of a person) slow to learn or understand things; not clever or intelligentHe'll manage—he isn't stupid.Forgetting my notes made me look stupid.She always makes me feel really stupid.3 [only before noun] (informal) used to emphasize that you are annoyed with somebody/somethingI can't get the stupid thing open!Get your stupid feet off the chair!stupidly
ˈstjuːpɪdli
 
; ˈstuːpɪdli
 
adverbI stupidly agreed to lend him the money.Todd stared stupidly at the screen.