stupid is as stupid does
Stupid behaviour indicates stupidity.
1882 Anthony Trollope: Orley Farm As long as a man can pay twenty shillings in the pound and a trifle over, what does it matter if all the judges in the land was to call him stupid
VERBS
appear, be, feel, look, seem, sound
He seemed stupid for forgetting his keys inside the locked car.
act
When the teacher asked a difficult question, he decided to act stupid instead of admitting he hadn't studied.
ADV
bloody
damn/damned, exceptionally, extremely, fucking
That was an exceptionally stupid mistake to make right before the exam.
incredibly, monumentally, particularly, really, very | absolutely, completely, (just) plain, utterly
not entirely
He's not entirely stupid, but he definitely made a foolish mistake this time.
a bit, a little, pretty, quite, rather
enough, sufficiently
She was stupid enough to lend money to someone she'd just met.
crassly, grossly
He made a grossly stupid decision by investing all his savings in that scheme.