Green’s Dictionary of Slang

1. the gallows.

c.1698		B.E. Dict. Canting Crew n.p.: [...] the Cull was glimm’d, he gangs to the Nub, c. if the Fellow has been Burnt in the Hand, he’ll be Hang’d now.
1719		A. Smith Lives of Most Notorious Highway-men, etc. (1926) II [as cit. c.1698].
1725		New Canting Dict. [as cit. c.1698].

2. the neck.

1674		Head Canting Academy (2nd edn).
c.1698		B.E. Dict. Canting Crew n.p.: Nub The Neck.
1707		J. Shirley Triumph of Wit.
1725		New Canting Dict. [as cit. c.1698].
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1754		Scoundrel’s Dict. 18: A Neck – Nub.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
a.1790		H.T. Potter New Dict. Cant (1797).
1809		G. Andrewes Dict. Sl. and Cant.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1835		G. Kent Modern Flash Dict.
c.1850		Duncombe New and Improved Flash Dict.
1859		Matsell Vocabulum.

3. (UK und.) a farthing.

1725

Life and Glorious Actions of [...] Jonathan Wilde 26: In the Thieves Language, a Farthing is called a Neck or Nubb.

4. (US) an ugly or repulsive person.

1942		Berrey & Van den Bark Amer. Thes. Sl.
1972		Dahlskog Dict. Contemp. and Colloq. Usage 42/2: Nub, n. An ugly girl; an ugly or replusive person.

5. a cigarette.

1959

W. Hall Long and the Short and the Tall Act II: I slipped him half a dozen nubs!

6. (US drugs) a very small portion of a narcotic.

2021

T. Swerdlow Straight Dope [ebook] — Give me another nub [of heroin], then don’t give me anymore no matter what I say.