What does back up peen mean?

back up peen meaning in Urban Dictionary

the expression back-up peen derives from that arbitrary man jacking off in the back of porno flicks. He is just standing truth be told there and isnt in fact included and contains no feedback. This term is employed to describe somebody who does not have any input and is simply going out performing absolutely nothing and it is just following somebody else or it may be someone on tv whos in history and is not involved, same task.