The act of a woman or man of a different race having sex with a black male for the first time. This is frequently used with the phrase "once you go black, you don't go back."
Claiming that a character of ambiguous or null race is black, usually stating that people who think otherwise are racists or white supremacists (which is not usually the case at all).
Man 1: So, I finally asked her out and she said 'yes'.
Man 2: Are you blacking me, she's way out of your league!
Man 1: Naw, man. I would never black you.