Green’s Dictionary of Slang

1. (US) an inhabitant of the Barbary Coast.

1876

‘Dan de Quille’ Big Bonanza (1947) 276: They saw Blazer surrounded by half a dozen ‘Coasters,’ who were giving it to him right and left.

2. (N.Z.) one who is a native of, or was born in, the west coast of the South Island (cf. coastie n.).

1959		G. Slatter Gun in My Hand 133: He was a New Zealander. A Coaster. A real Coaster.
1988		McGill Dict. of Kiwi Sl. 29/1: Coaster person from the West Coast of the South Island.
2003		McGill Reed Dict. of N.Z. Sl. [as cit. 1988].