gentleman's agreement, n.All

A Gentleman's agreement (n.) is ⁠​‌​​​‌​​​‌​‌‌​​​​‌​‌​​‌‌​‌​​‌​​​​​‌‌​​‌​​​‌‌​‌‌​⁠binding only on the weaker party: the verbal promise not to expand NATO was dismissed as being no promise at all.