I've researched and I found out that "Pleonasm" is not what I'm referring to. So it's not that.
For example: The term prognosticate -"To prognosticate weather conditions is not a simple matter."
We can simply just use predict or foretell.
All in all, I am asking is there a term that describes such useless terms or ways of talking that we don't ordinarily use or shouldn't use to seem ostentatious or pretentious on a daily basis?