French leave

WordReference Random House Learner's Dictionary of American English © 2025

ˈFrench ˈleave, n. [uncountable]

1. an unauthorized departure.

WordReference Random House Unabridged Dictionary of American English © 2025

French′ leave′, 

1. a departure without ceremony, permission, or notice:
   Taking French leave, he evaded his creditors.

• 1765–75

Collins Concise English Dictionary © HarperCollins Publishers::

French leave noun

1. an unauthorized or unannounced absence or departure

Etymology: 18th Century: alluding to a custom in France of leaving without saying goodbye to one's host or hostess