Underground Pipe 

verb. : A euphemism for the brown surprise, or butt sex.

There were alot of guys trying to lay underground pipe in the Manhole bathroom on Halsted.

Underground Pipe by FFJeroni January 20, 2011

Underground Rap Pipeline 

A pipeline of a rap fan, in a effort to find more underground or niche rap music, ending up exponentially listening to more and more experimental and "unlistenable" music.

Dude 1: Bro have you heard that new Edward Skeletrix?

Dude 2: Dude he sucks you are deep in the Underground Rap Pipeline

Underground Rap Pipeline by Apollo1721 October 9, 2025