A simple, yet sexy word to describe the most erotic of moments between two, or more people (as well as, on occasion, one large person). This, so far, is a word known only in the south of Scotland and certain parts of Australia. It means sex, drugs, rock n' roll and erotic bathing. The original source (person / thing) is, as is often the case, lost in the mists of time / steam of the bathroom.
The best examples of Quinnbath are found in music. The songs "Gay Bar" by Electric Six and "Love Shack" by the B52's have famously been amended, with the every mention of the title replace with "Quinnbath". There are countless other examples, but these are the best and, as a result, the best known.