When one's arms are particularly large; the muscular state of one's arms after a workout....Derived from the word "pipes", referring to the arms.
Sean: "Shiiiiit, I gotta wrestle Dan next week in the sectionals."
Max: "No easy task there, dude. Saw him last week. I don't know if he'd just come from the gym or what, but that mofo was all piped up."