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.
If a girl is having sex with one guy for an extended period of time but are not dating, and he goes home for the weekend, she resorts to her side pipe. This is a guy that she has banged before, but has not lead anywhere, and she keeps him on the back burner when needed.
When an individual of the male persuasion in an institutional circumstance (i.e. work, school, etc.) becomes sexually aroused, due to thoughts of past sexual exploits; the subsequent tightening of the groin area, due to the constriction of pants upon the hardened member, produces a penile-angular shift, which is almost perfectly horizontal in form, and points towards either the left or right. Thus the moniker, Side-Pipe.
Mosieur LePajonais: What, pray tell, is that tubular formation protruding from the side of your pantaloons?