Green’s Dictionary of Slang

(orig. US) a sweetheart, a boyfriend, a husband.

1893		Seattle Post-Intelligencer (WA) 15 Jan. 11/2: A pert little maiden remarked [...] ‘Carnations and love will do for some girls; but I have educated my best boy up to orchids’.
1900		Sporting Times 9 June 1/3: Even after I managed to get out to my best boy in the picket lines there was the blessed old searchlight on us the whole night!
1905		‘Doss Chiderdoss’ ‘A Dual Ownership’ Sporting Times 4 Feb. 1/4: Not exactly engaged, but I have a best boy, who I’m told has been rather a rake.
1910		Sporting Times 8 Jan. 2/4: Your best boy of the moment is trying to give you the meal of your life.

describing a woman with a voluptuous figure.

2003

Impact Internet Services ‘The Movie Pages’ on ImpactServices.net.au 🌐 ‘Rev. of Shallow Hal’ [...] You see as a young kid his dying father left him with an important message that he should always make sure that he only settles for the best looking and best built woman.

(orig. US) a sweetheart, a girlfriend, a wife.

1884		Northern Trib. (Cheboygan, MI) 3 Apr. 7/1: ‘I lent my best girl to Jones yesterday,’ said Brown to his friend. ‘Lent your girl, what do you mean?’.
1890		Sporting Times 12 Apr. 7/2: The best girl sends me one occasionally, and they go the rounds.
1894		Courier (Lincoln, NE) 20 Oct. 17/2: Demmed if I don’t think that my best girl considers me slow, b’Jove.
1900		Flynt & Walton Powers That Prey 211: Don’t you want to give me back that watch? My best girl gave me that.
1910		‘Doss Chiderdoss’ ‘Bella’s ‘Best Girl’’ Sporting Times 23 Apr. 1/3: ’Twas guessed so by her friends when they were told / That her best girl was his best girl first of all!
1915		Bismark Dly Trib. (ND) 26 Sept. 4/3: ‘My Best Girl’ — the scintillating comedy drama that is proving a big hit.
1917		F. Packard Adventures of Jimmie Dale (1918) II vii: I believe some chauffeurs have a habit [...] of taking, shall we say, their ‘best girl’ out riding in their masters’ machines?
1965		B. Jackson Get Your Ass in the Water (1974) 88: [They’ve] kicked your best girl out in the streets and sold all the fixtures in your flat.

the vagina.

1890–1904		Farmer & Henley Sl. and Its Analogues.
1896		Farmer Vocabula Amatoria (1966) 36: Bête (la), f. [...] The female pudendum; ‘the best-worst part’.

see shot n.¹ (5a)

see under leg n.