An
extravagant or
grandiose (hence the name) word used in place of a much
simpler,
commonly-used one. Not neccesarily a
euphemism or a
cacophemism.
Lexicographers,
linguists,
Scrabble players, and
stuck-up twits primarily
benefit from the usage of these.
Oddly enough, the word is a grandiloquism itself. Use them when you
aim to :
A) confuse,
B) impress, or
C) piss off people.
The few of us who actually like to use grandiloquisms for reasons other than the above should quit being such bastards and stop reading the dictionary like it's porn.