Padded shorts used for biking, also known as a chamois. Feels like a full wet diaper when you sit down after a long bike ride, but instead of urine, it's wet with crotch sweat.
Person 1: "good ride, man."
Person 2: "Yah, that was a long one. I really need to go change my biker diaper."
Person 1: "gross.... Me too...."