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English definition of “fail”

fail

verb [I/T] (NOT DO)   /feɪl/
to not do something that should be done: [+ to infinitive] He promised to help, but failed to send a check. [+ to infinitive] She never fails to meet a deadline. To fail is also to not help someone when expected to: [T] He failed her when she most needed him.
(Definition of fail verb (NOT DO) from the Cambridge Academic Content Dictionary © Cambridge University Press)
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