Green’s Dictionary of Slang

1. (US teen) an unattractive female.

1968

H. Sebold Adolescence 250: Girls are judged very harshly. The girl who is pegged as a scab, a shank, a bat, or an ox may be shattered forever.

2. (N.Z. prison) second-rate heroin [? ext. of sense 1., but note cut v.⁶ (4b)].

1999		D. Looser ‘Boob Jargon’ in NZEJ 13 35: shank n. 1. Bad quality heroin.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 163/1: shank n. 2 heroin of poor quality .