Green’s Dictionary of Slang

1. (US) a hanger-on.

1970

in DARE.

2. (UK Black/gang, also blocka) a friend, lit. one who lives in the same (tower/council) block as oneself.

2015

67 ‘Trapping’s Alive’ 🎵 Ride with my blockas, and I ride on my solos.

3. (N.Z. prison) in a female prison, a woman who rapes other women.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 21/1: blocker n. a woman who rapes other women, i.e. puts them on the block.