When someone uses big words despite the fact that they:
-Sound unnatural saying them
-Don't know what the words mean
-Didn't need to use such complicated words to get their point across
-Are really dumb, and try to sound smart by saying them
Tom: I have just explicated your histrionics you boondoggling pantimime!
Jake: And you are also guilty of thesaurus rape....
The use of "big" words in lieu of their "common" counterparts (often out of context) in a futile attempt to sound more intelligent. This technique is often used by liberal arts students when attempting to sound competent when talking about a subject that they have no clue about.
In a class room discussion about UrbanDictionary.com
Jill: Urban Dictionary's abominable nature not only proliferates the use of exiguous, diminutive, colloquial English, it actually bolsters and espouses it!
Jack: ya, and it gives us words like thesaurus rape to describe what you are doing!!