Green’s Dictionary of Slang

master n.

1. (US black) the absolute best; also as adj.

[US] in N.E. Eliason Tarheel Talk (1956) 283: In the mountain a hunter says ‘It was a “Master” bear, a “Master” fight, a “Master” tree,’ meaning the largest or best or greatest.
[US]Bentley & Corbett Prison Sl. 50: Master The ultimate or absolute best. Master may refer to people, drugs or a productive way in which a prison sentence is served.
[Ire]G. Coughlan Everyday Eng. and Sl. 🌐 Master (n): the best, expression of approval. ‘It’s the master.’.

2. (NZ prison) constr. with the, a male visitor, a female inmate’s male partner.

[NZ]D. Looser ‘Boob Jargon’ in NZEJ 13 36: the master n. Male visitor/partner.

In compounds

SE in slang uses

In compounds

master-can (n.) [can n.1 (4b)]

a chamberpot.

D. Herd Collection ii, 214: She hae dung the bit fish off the brace, An’ it’s fallen i’ the maister-can [F&H].
master of… (n.)

see separate entry.

master-piece (n.)

1. (Aus. Und.) a tool used by a thief, ? a crowbar, ? a set of skeleton keys.

[Aus]W.S. Walker In the Blood 143: With ‘master piece’ in kit, I often do a bit.

2. see separate entry.

master vein (n.)

see separate entry.