Green’s Dictionary of Slang

1. a worn-out old prostitute.

1972		R.A. Wilson Playboy’s Book of Forbidden Words 137: The lowest class of prostitutes [...] are known as [...] tanks.
1984		Partridge DSUE (8th edn) 1202: from 1918 or 1919.

2. (US Und.) a bulletproof car.

1933		Ersine Und. and Prison Sl.
1949		Monteleone Criminal Sl. (rev. edn).
1969		D. Pendleton Executioner (1973) 77: ‘It’s a tank, all right,’ Bolan grunted to himself, noting the battering-ram writhing of the Rolls.

3. (US black) a streetcar.

1942

D. Burley N.Y. Amsterdam Star-News 7 Feb. 16: [They] were gunning the stroll from a layout [...] where the tanks cop a roll.

4. (US campus) an unattractive female.

1966		Current Sl. I:2 6/1: Tank, n. A very unattractive female.
1979		B. Gutcheon New Girls (1982) 76: Now they would find her a pig, a tank.

5. (Aus.) a four-wheel drive automobile.

2005

P. Temple Broken Shore (2007) [ebook] He remembered seeing bullbars, the nose of a big four-wheel drive [...] Cashin saw the tank gun out of the gate and swing right.

6. (US) a worn-out automobile.

2015		L. Berney Long & Faraway Gone [ebook] The Cadillac, a tank, didn’t have a scratch on it.
2019		C.D. Rosales Word Is Bone [ebook] [He] knows I have this old tank, this van I used to use as the roach coach.