Green’s Dictionary of Slang

1. (US black) the killing of a female.

1997

G. Sikes 8 Ball Chicks (1998) 14: Guys still shoot a female in a flash — it’s called a ‘bitch slap’.

2. (orig. US prison) a slap rather than a punch with the clenched fist; the implication is that the victim isn’t ‘man enough’ to deliver a proper blow.

1999		Guardian G2 15 June 17: Sparing us the ten-man bitch-slap which would surely erupt.
2002		J. Lerner You Got Nothing Coming 248: In prison bitch-slap brings the added burden of humiliation to the recipient [...] You ain’t nothing but a punk-ass bitch, so this time you’re getting a litle bitch-slap. Dis me again, motherfucker, and you’re dead!
2006		F.X. Toole Pound for Pound 116: Mr. George wanted to give Sykes a bitch slap.
2012		T. Robinson ‘Legendary [...] Ralphie O’Malley’ in Dirty Words [ebook] For Ralphie, it [i.e a piece of bad luck] was just another bitch-slap from hell.
2021		T. Swerdlow Straight Dope [ebook] [E]very sordid deed and savage act of self-violence: every grunt, groan, bite mark and bitch-slap,.

3. (N.Z. prison) an inxperienced and/or low status prisoner.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 19/1: bitchslap n. an inmate of low status, regarded as inferior; particularly applied to an inmate who has served little time in prison.