The end result of prolonged bouts of male masturbation and ejaculation into a tube sock used as a gak towel.

The sock becomes stiff and rigid like a plaster cast. And as they say, it can stand up all by itself.

Usually found under the beds of teen males by their unsuspecting mothers.
Roger yanked off so much into his tube sock that he turned it into a plaster cast.
by Eaton Holgoode August 4, 2016
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a big, hot 'n' heavy article of healing that most people assume is for broken bones. In reality, it is something to be worn on your right leg to the knee for four months after surgery when you've taken out a garbage back with a huge piece of broken glass in it, banged said garbage bag into your leg, and severed your achilles tendon (and have to miss all the swimming for the entire summer). You will recognize a 'plaster cast' by the painting on it of a small little dachshund known as kira.
Jerk on the street: Hey, nice plaster cast - I can tell by the kira painting. But why the hell are you wearing that heavy artwork all summer long?
by sea ryder August 2, 2006
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