Mumpsimus is an odd word which, in simple terms, means the erroneous use of language or expression.
Here's the official dictionary description of the word:
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).
1520–30; from a story, which perhaps originated with Erasmus, of an illiterate priest who said mumpsimus rather than sūmpsimus (1st plural perfect indicative of Latin sūmere to pick up; see consume) while reciting the liturgy, and refused to change the word when corrected.
So, what do you think of this word? Can you use it in a sentence?