expression, godan verb (-ru)
lose face as a man; bring shame on oneself as a man
Idiomatic expression used when a man's action or situation damages his dignity, honor, or reputation. Often used in negative or conditional forms (e.g., 男がすたるようなことはしない).
そんな小さなことで怒ったら男がすたる。
A man loses face if he gets angry over such a small thing.
約束を破
Breaking a promise is the kind of act that brings shame on a man.