expression, godan verb (-ru)
break a promise; go back on one's word; renege
Direct expression for failing to keep a promise. Often used in personal or informal contexts. Cross-referenced with the more common 約束を破る, which is the standard form with the object marker を.
See also: 約束を破る
彼は簡単に約束破るから、もう信じられない。
He breaks promises so easily that I can't trust him anymore.
約束破るようなことはしないでほしい。
I hope you won't do something like break your promise.