Pronunciation: (mump'su-mus), [key]
—pl. -mus•es for 2.
1. adherence to or persistence in an erroneous use of language, memorization, practice, belief, etc., out of habit or obstinacy (opposed to sumpsimus).
2. 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.