Ride the Peg means for a guy to sit on the raging hard-on of another dude's dick and move his body up, down, and all around, while jacking off until they both have cumgasms and blow their loads -- best if another guy is also fucking his mouth.
When a girl is giving you head and you shoot it in her mouth then you punch her in the eye and stomp on her foot. She is hopping around on one foot holding her eye just like a pirate with a peg leg.
After I shot it in her mouth I gave her the peg leg pirate!!!