/ Thesaurus / M Synonyms of mental exhaustion Find synonyms for: Noun1. mental exhaustion, brain-fag, exhaustionusage: exhaustion that affects mental keennessWordNet 3.0 Copyright 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: diurnal Analogy of the Day: Today?s Analogy Spelling Bee: Today?s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language