When one man stelthely approaches another man from the side and rubs his man parts against another man's side. The man then shouts"Side Pipe". This activity typicaly takes place on Saturdays to celebrate "Side Pipe Saturday" .
Background: These types of games evolved from "Man Love Monday" where heterosexual men isolated from women while working in the logging camps of North Central West Virginia playfully turned to one and other to cope with isolation and lonleiness.
While Standing in the lunch line Rich snuck up on Mike and side piped him.