- (subordinating) except under the circumstances that; except on the condition that: they'll sell it unless he hears otherwise
WordReference Random House Learner's Dictionary of American English © 2019
- except under the circumstances that:We'll be there at nine, unless the train is late.
- except under the circumstances that:I'll be there at nine, unless the train is late.
save:Nothing will come of it, unless disaster.
- 1400–50; late Middle English prepositional phrase on less (also o less(e), earlier upon less) on a lesser footing or condition (than); first used as a preposition and conj. in the early 16th century; see on, less