Green’s Dictionary of Slang

(US black) to dismiss something as no longer important or relevant.

1969		L. Schecter Jocks 1157: [H]is quick ability to recognize and obliterate (yes, that’s the word; he sort of x’d them out) the sycophants.
1992		R.C. Cruz Straight Outta Compton n.p.: He appears glassy-eyed while pointing his index in my face, ready to X me out.