Green’s Dictionary of Slang

yo n.

[yo! excl. (2)]

1. (US) a young black man, esp. one who deals drugs on the street; thus fem. yoette.

[US]D. Simon Homicide (1993) 324: Clayvon Jones is simply a dead yo. [Ibid.] 350: Some sweet-voiced yoette wailing out the [...] lyric.
[US]Simon & Burns Corner (1998) 478: Paler-skinned hillbillies and hard-faced yos, toothless white trash and gold-front gangsters.
[US]Simon & Burns ‘Old Cases’ Wire ser. 1 ep. 4 [TV script] Fuckin’ yo did you a favour.
[US]G. Pelecanos Night Gardener 101: Maybe [...] the victim had been hitting some other yo’s girlfriend.

2. attr. use of sense 1.

[US]Simon & Pelecanos ‘Amsterdam’ Wire ser. 3 ep. 4 [TV script] (of a mobile telephone) The latest in yo-tech.