something won't wash

not wash

To not be accepted or believed. That kind of excuse may have worked in high school, but it doesn't wash with me. The deadline for the paper is tomorrow, no extensions. He may be able to skirt the issue in some regions, but that approach won't wash in these parts—these people want straight answers.
See also: not, wash
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

something won't wash

If an explanation or idea won't wash, it will not be believed or accepted. Mr Aitken might try some such explanation if and when he returns. It won't wash. It won't wash to claim that what we eat is purely a matter of personal responsibility.
See also: something, wash
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012

something won’t/doesn’t ˈwash (with somebody)

used to say that somebody’s explanation, excuse, etc. is not valid or that you/somebody else will not accept it: That excuse simply won’t wash with me.
See also: something, wash
Farlex Partner Idioms Dictionary © Farlex 2017
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