The opposite of underexaggeration (truth).
Overexaggeration differs from mesoexaggeration (commonly known simply as "exaggeration") in that mesoexaggeration
strays from the truth to balance out
skepticism, while
overexaggeration goes beyond this to a non-believable, completely ridiculous extreme.
(actual example)
Tim: Me and my brother Joe took out four guys at this UFC fight thing. I can
bench press 225 pounds. I got a 25...wait a 26...wait a 27 on the ACT.
Me: Tim, let's have a chat about this thing called
exaggeration. Or, in your case, overexaggeration.