A potentially painful condition in which a male, often wearing boxers or no underwear, is walking or jogging and the testicles and/or flaccid penis repeatedly slaps against the inner thighs.
Jogger Chad: "Dude... ok, I gotta take a break here..."
Jogger Michael: "Aw, man come on... we got three miles to go."
Jogger Chad: "Dude... fucking got pendulum penis going on right now, k? Gimme a freaking break."
Jogger Michael: "For Christ's sake, you said that two minutes ago."
Jogger Chad: "Fuck off! I thought I had the testies
of Papa Smurf last time I tried to tough it out... couldn't beat off for two days."