Penis Promise 

A promise made while your penis is inside a person to that other person. Akin to pinkey promise but it is ten times a legit.

Justin: "Oh god I want to spend the rest of my life with you!"

Megan: "Swear?"

Justin: "Penis Promise."

Megan: "Good."

Penis Promise by Fallenrook1989 July 20, 2010

Penis Promise 

When two men wrap they're dicks together and make a promise

Do you penis promise you won't fuck the dog anymore?

Penis Promise by big hairy nutsack 3 August 18, 2019