Definition of "cottaging"
(Britain, slang) Sexual activity in a public lavatory, especially homosexual activity between men.
Quotations
"MSM," a term that is reportedly English social-work jargon for "men seeking sex with men," explores the reasons why men, including heterosexuals, cruise in English lavatories, which are, believe it or not, called "cottages." The text is made up of actual interviews with those who go "cottaging."
1993 October 6, Anna Kisselgoff, “Upstart and Formal Styles in Montreal”, in The New York Times, page C14