Green’s Dictionary of Slang

1. (US) a promiscuous or socially frowned-upon woman; also attrib.

1933		W.R. Burnett Dark Hazard (1934) 194: Then you won’t be throwing chairs around and drinking booze and acting like a lot of alley cats.
1942		Berrey & Van den Bark Amer. Thes. Sl. §439.2: Slut, alley cat.
1946		D. Burley N.Y. Amsterdam News 26 Jan. 21: [T]hree young women fighting like alley cats.
1987		R. Campbell Alice in La-La Land (1999) 98: For Christ’s sake, this is a town full of alley cats.
1998		‘Bill E. Goodhead’ Nubile Treat 🌐 Now I know where Mom gets that alley-cat quality of hers, he thought.

2. (US) a prostitute.

1942		Berrey & Van den Bark Amer. Thes. Sl. §507.2: Prostitute, alley cat.
1949		Monteleone Criminal Sl. (rev. edn).
1972		R.A. Wilson Playboy’s Book of Forbidden Words.
1989		H. Rawson Dict. of Invective (1991) 73: the alley cat. A person with relaxed sexual standards; one who has the morals of an alley cat; specifically, a prostitute.
1993		I.L. Allen City in Sl. (1995) 46: An utterly fallen woman, especially a lower-class one, is an alley cat who, following the metaphor, roams back alleys.

3. (US) a street urchin.

1942

Berrey & Van Den Bark Amer. Thes. Sl. §418.2: Ragamuffin, alley cat.

4. (US) a womanizer.

1933		Hecht & Fowler Great Magoo 99: If that ungrateful alley-cat shows up here will you tell him to get off his bicycle and come home.
1949		Monteleone Criminal Sl. (rev. edn).
1953		K. Tennant Joyful Condemned 205: Geechi! [...] You ole alley-cat! Where you been?

5. (UK Und.) a nightwatchman.

1931

‘Und. “Lingo” Brought Up-to-Date’ L.A. Times 8 Nov. K3: ALLEY CAT: A private watchman.