look up any word, like thot:
 
2.
When someone takes away from your high, or tries to be cool by fucking with you when you are buzzed. What happens when a nancy (see Nancy) brings down your elated feelings while high.
Dude, you're really harshin' my mellow.
by Duke March 13, 2005
 
1.
Bringing down my good mood.
I didn't like her.. she was really harshing my mellow, man.
by Julia May 07, 2005
 
3.
A stupid idiom that Mackenzie wants to believe is real, when it really isn't.

This isn't a real phrase and has been completely made up.
Mackenzie:
What does "harshing my mellow" mean?

Anyone who isn't an ignoramus:

It doesn't mean anything, because you just made that phrase up and it doesn't exist.
by American Dictionary of Idioms. April 10, 2011