caster, adj. — Green’s Dictionary of Slang

caster adj.

(N.Z. prison) used to imply positive qualities.

1982		G. Newbold Big Huey 246: Caster (adj) Good, OK, fine.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 38/1: caster adj. good, fine, okay .

In phrases

Caster Master (adv.)

(N.Z. prison) well, positively.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 38/1: Caster Master adj. good, fine, okay: ‘How are you going?’ ‘Caster Master’ .

Caster McNarster (phr.)

(N.Z. prison) a warning to a fellow-inmate that an officer is watching them.

2001

D. Looser Boobslang [U. Canterbury D.Phil. thesis] 38/1: Caster McNarster an expression warning an inmate that he is safe at present, but there is an officer watching his activity.