/ Dictionary / Index M mumpsimus: Meaning and Definition of Find definitions for: mump•si•mus Pronunciation: (mump'su-mus), [key] — pl. -mus•es adherence to or persistence in an erroneous use of language, memorization, practice, belief, etc., out of habit or obstinacy (opposed to sumpsimus). a person who persists in a mistaken expression or practice (opposed to sumpsimus). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: mumpsimus (Thesaurus) mumps mumu Related Content Daily Word Quiz: panacea Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language