Green’s Dictionary of Slang

1. (US) an attractive young woman; also as affectionate term of address (to man or woman).

1939		D. Runyon in Collier’s 6 May 9: I never see a prettier little cupcake than this nurse.
1945		R.L. Bellem ‘Coffin for a Coward’ in Hollywood Detective Dec. 🌐 The taffy-haired cupcake might have had more than a patriotic reason for losing her temper, too.
1975		L. Rosten Dear ‘Herm’ 101: This cup-cake doesnt wear no ‘bra’ neither.
1986		C. Hiaasen Tourist Season (1987) 311: All right, cupcake, if you’ll sleep easier.
1992		K. Lette Llama Parlour 16: Got it, cupcake?
1996		Dandy Book n.p.: ‘What’s that you’re reading, cupcake’.
2000		(con. 1940s–60s) Décharné Straight from the Fridge Dad.
2013		T. Robinson Hard Bounce [ebook] ‘How’s it going, cupcake?’.
2023		(con. 1962) J. Ellroy Enchanters 336: Bo: ‘Wow. Marilyn Monroe’s lover, huh?’ Liz: ‘Es la verdad, cupcake’.

2. (US) usu. in pl., the female breasts.

1971		(con. 1960s) D. Wells Night People 107: She’s only the baker’s daughter, but, oh, how I’d love to nibble her cup cakes!
1981		G.V. Higgins Rat on Fire (1982) 106: This drunk comes up to you in the bar [...] and he gets a look at the cupcakes.

3. (US gay) a young homosexual man.

1972		B. Rodgers Queens’ Vernacular.
1992		Bentley & Corbett Prison Sl. 59: Cup Cakes A homosexual, primarily a passive one. (Archaic: fruit).

4. (US gay) in pl., buttocks, esp. when tight, firm and small.

1971		F. Hilaire Thanatos 136: Each of the faces was now cheering and whistling, all in gratitude for Leslie’s wantonly gyrating hips. [...] ‘Hey, Sammy, tell the girlie [homosexual man] to save me some of them cupcakes!’.
1972		B. Rodgers Queens’ Vernacular.
1988		H. Max Gay (S)language.
1989–2003		R.O. Scott Gay Sl. Dict. 🌐.