Green’s Dictionary of Slang

(US) revenge.

1905		‘Hugh McHugh’ You Can Search Me 92: ‘I wish you could have seen our place in daytime,’ Peaches was saying to Skinski when I finished reading Bunch’s get-back.
1994		N. McCall Makes Me Wanna Holler (1995) 4: We called it [i.e. beating white people] ‘gettin’ some get-back’.
2002		J. Lerner You Got Nothing Coming 102: Kansas unleashes a virulent [...] stream of obscenities, flavored with his fervent promises of ‘getback’.
2008		G. Pelecanos Way Home (2009) 93: The boys from Calvin’s unit would have been out for revenge [...] There would have been eye-mugging, shoulders brushes, talk of get-back.