expression, godan verb (-tsu)
to be slightly offended; to be somewhat irritated
A rare expression meaning to feel a mild, petty annoyance. Compared to 腹が立つ, it suggests a smaller, less serious irritation.
See also: 腹が立つ
彼の言い方に小腹が立ったが、言い返すほどではなかった。
I was a little irritated by his way of speaking, but not enough to talk back.