n. a stupid-acting person. : I always end up with a mouth-breather on a blind date.
Dictionary of American Slang and Colloquial Expressions by Richard A. Spears.Fourth Edition. Copyright 2007. Published by McGraw Hill.
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Main Entry: mouth breath·er Pronunciation: -"brE-th&r Function: noun : one who habitually inhales and exhales through the mouth rather thanthrough the nose