The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with alley cat
A promiscuous woman; also, a person of loose morals. For example, She's constantly picking up men in bars—a real alley cat. This idiom transfers a stray cat that frequents alleys in search of food to a woman of easy virtue, especially a prostitute seeking customers.
[ ; early 1900s