A "Rotten Scotsman" is acheived when a woman inserts her thumb into a man's anus, squeezing and releasing his testicles with one hand, and sucking and strocking his penis with her mouth and other hand. The action gives the look that she is playing the bagpipes.
Last night when Sue was giving me a blow job, all of sudden she shoved her finger up my ass and sqeezed my balls, all with the same hand. I asked her what the hell she was doing, and she said, "I'm giving you a Rotten Scotsman!"
by Billy Madison June 5, 2003