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1.
what you get when you wear old pants, especially jeans
I thought his looked great, but i've got sag-ass.
by mr juggly May 11, 2013
 
2.
When the back of your jeans sag down creating excess baggage.
Tim: Yo Gabe, those new jeans?
Gabe: Ya why?
Tim: I thought you were a 34x32 not a 34xSag Ass
by BobMitchell(.)(.) January 11, 2011