Green’s Dictionary of Slang

1. a drinking club, a friendly gathering.

1800		Sporting Mag. Oct. XVII 41/1: Then at the libraries, the rattling dice / The old, the young, the rich, the poor, entice.
1984		Partridge DSUE (8th edn) 679: ca. 1640–90.

2. (US, also outdoor library, reading room, Sears Roebuck library) a privy [the old catalogues, newspapers etc. that were often left there as lavatory paper; the common use of old Sears catalogues as lavatory paper].

1931–33		LANE Worksheets n.p.: Library — Outhouse [DARE].
1949		in PADS [DARE].
1965–70		in DARE n.p.: [...] Library; [...] Outdoor library [...] Sears-Roebuck library.
1973		(con. 1950) H.B. Allen Linguistic Atlas of the Upper Midwest 1.181: Privy [...] library [DARE].
1984		Eble Campus Sl. Mar. 4: library – bathroom. Synonym: Reading room.

3. (US) an ‘adult’, i.e. pornographic bookstore.

1999

Gaymart.com Queer Sl. in the Gay 90s 🌐 Library – An adult bookstore.