Green’s Dictionary of Slang

1. (orig. US black, also base on) to disparage, criticize or humiliate another person.

1972		E. Folb Urban Black Argot 133: to Base On Someone, to verbally disparage.
1980		E. Folb Runnin’ Down Some Lines 95: You get to basin’ more or less put a man or woman in dey place [...] Righteously blow d’ brother’s stuff away, jus’ steadily scream on someone like dey done sumpin’ to you and you righteously mad at ’em. [Ibid.] 228: base (on one) Disparage, ridicule, or confront another.
1988		Eble Campus Sl. Oct.
1989		P. Munro Sl. U. 28: Base on, to criticize.

2. to argue.

1990		N.Y. Mag. 28 May 27/1: [black high school slang] Kids ‘basing’ are arguing.
1993		Lerner et al. Dict. of Today’s Words.