1to irritate or exasperate someone; to provoke annoyance (transitive).
彼の遅刻は皆の気持ちを苛立てた。
His lateness irritated everyone's feelings.
無神経な発言で同僚を苛立ててしまった。
I irritated a colleague with an insensitive remark.
その機械の連続音が耳につき、苛立てる。
The machine's continuous noise gets on your nerves and irritates.