I'm on yo ass

User of the phrase: is about to begin or is already in the process of joking about/ dissing the receiver of the phrase.

Synonym Phrase: I'm about to roast on you.

Somewhat of a taunt or gloat.

Example 1

Guy 1: "Hahaha! Is that fake Polo?"

Guy 2: "Oh you, tryna' roast? Bruh I'm on yo ass! Ol, high water, flipped collar, no dollar lookin' boy!"

Example 2

Guy 1: "That's what yo momma said when she left last night!"

Guy 2: "Shut up man! yeen funny!"

Guy 1: "Hahaha! Boy I'm on yo ass!"

I'm on yo ass by Zip Zack November 27, 2012

I'm kool on yo ass 

when you feel like beating a trick down or getting them told, but the present circumstance doesn't permit you to, but it is understood that that ass will get got

Meredith, I can't believe you brought up what I did in front of the boss, but you know what I'm kool on yo ass.

I'm kool on yo ass by Snap Crackle Pop February 26, 2008