adverb, noun or participle which takes 'suru'
get suddenly irritated; get annoyed
Colloquial adverb describing a sudden flash of irritation or annoyance. Often used with する to mean 'to get irritated' or as an adverbial modifier.
彼の一言にイラっとした。
I got irritated at his remark.
イラっとするけど、我慢しよう。
It's annoying, but I'll put up with it.