과민해요 · 과민했어요 · 과민한 (+noun)
to be oversensitive, hypersensitive
Example
제가 그 말에 너무 과민하게 반응했나 봐요.
I guess I overreacted to that comment.
Word parts
과 excessive+민 sensitive
Literally 'excessively sensitive'.
Good to know
Very common in 과민 반응 (overreaction) and 과민성 대장 증후군 (irritable bowel syndrome).