thirteen, n. — Green’s Dictionary of Slang

thirteen n.

1. (drugs, also 13) marijuana [the initial letter M, 13th in the alphabet].

1966		H.S. Thompson Hell’s Angels (1967) 121: Among the first to be exposed was the numeral ‘13’ (indicating a marijuana smoker).
1971		E.E. Landy Underground Dict. (1972).
2001		ONDCP Street Terms 21: Thirteen — Marijuana.

2. see thirteener n.

SE in slang uses

In phrases

thirteen and a wash-out (n.) [the supposed unluckiness of thirteen; the wash-out n. (1) is death; some prisons, using hanging, have thirteen steps onto the gallows]

(US prison) the execution chamber.

1931		G. Milburn ‘Convicts’ Jargon’ in AS VI:6 441: Thirteen-and-a-washout, n. The death house.
1949		Monteleone Criminal Sl. (rev. edn).
1951		Montgomery Advertiser (AL) 23 Sept. 37/4: In soda-jerker slang, thirteen means ‘the boss is coming;’ ‘thirteen-and-a-washout’ is a jargon used by prisoners in reference to the death house.

thirteen and the odd (n.) [ety. unknown]

a tail-coat, as worn with ‘white tie and tails’.

1911		G. Bronson-Howard Enemy to Society 232: Ain’t you dining out? What’ll I git you — the ‘soup-and-fish’ or the ‘thirteen-and-the-odd?’ Stephen disclaimed any desire for the dinner coat first mentioned, declaring his preference for the more formal tailed garment.
1919		Van Loan ‘His Own Stuff’ in Score by Innings (2004) 384: The old thirteen-and-the-odd. Claw-hammer, white tie, silk hat and the rest of it.
1935		A.J. Pollock Und. Speaks.

thirteen to the dozen (n.)

see forty to the dozen adv.