The past verb or past participle of:

deprecate. n. To express earnest disapproval of; to belittle.
by Bad Grammar Must Die April 2, 2003
To fuck it off completely. Generally used by those understanding of the modern idiosyncrasies of the evolving nature of the English language.

It has nothing to do with any of that 'expressing disapproval' crap...
"Im going to deprecate that B1 shit"
by definitely_not_me February 5, 2014
Insulting; devaluing; or belittling oneself, often in a sarcastic or humorous way.
Young girls are so self deprecating. They never talk about anything but their flaws.

Tate: I have to cancel our plans this weekend!
Lana: Don't worry about it; I'm an expert when it comes to spending weekends alone.
Tate: You're so self deprecating sometimes, Lana.
by Kellyisawin! December 3, 2013
belittling one's self: the act of belittling yourself or your achievements
She has low self-esteem and is prone to self-deprecation.
by BobTheMan October 17, 2005