Unwanted and excessive jiggling and swinging of the male genitalia during pelvic thrusting, often caused by the lack of restrictive underwear. Sometimes causes nausea or vomiting in others.
Girl #1: Did you see Johnny dancing last night? He had a seriously disgusting case of floppy junk going on.

Girl #2: Yeah, it made me want to blow donkey chunks. Jesus, buy some boxer briefs, dude.
by floppyjunkistheenemy February 27, 2008
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