It means one who is ignorant of the true meaning of a word. A person who repeatedly misuses a word or group of words or one who incorrectly defines a word or a group of words. Usually implies one who does so unintentionally but with a flagrant disregard for the true origin of a word.
Derived from the modern words etymology (the study of speech & word origins) and moron (one who is foolish, and lacking in intelligence).
The Urban Dictionary's rating system helps keep the etymorons in check.
My friends are always trying to come up with cool 'new' words but they just end up sounding like a bunch of etymorons.
Bill's etymoronic tendencies can be embarrassingly awkward at times.