Person 1: I was walking the other day and I saw a... uhh.. a Zipperdude. Can you believe it I saw this really big Zipperdude!
Person 2: What's a Zipperdude? What are you talking about? What is it?
Person 1: It's not anything. It doesn't have a definition.
Person 2: You can't use a word that doesn't have a definition!
The bulge formed in a man's genital area, caused by sitting down with jeans. The zipper bunches up, forming an erection like bulge, which can scare and excite all who are there to witness it.
"FUCK, IT'S JUST CAREERS CLASS DON'T GET ALL EXCITED ON ME"
"Calm down man, it's just a zipperection."
"Oh. Haha, it's pretty funny."
The misleading, bulge-y shape created by a warping zipper in your clothing that makes it look like you have a hard-on underneath the protruding garment, giving it its charming name. This phenomenon is known to strike in pants, hoodies, and many other articles of clothing, especially when bunched up / sitting down.
Kristin : OMG Steven is that a full-chub??!!
Steven : No no I swear!! It's not a boner - it's my zipper, look!
{Goes to press down the fabric to demonstrate the vacancy of engorged member}