A solid piece of poop blocking the butthole passage allowing prolonged control over otherwise explosive diarrhea.
Adam blew his poop cap, and now he can't stop shitting everywhere!
by Plumpy4000 December 22, 2007
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When you're taking a shit, and the initial shit is a regular solid one, but everything that follows after is pure diarrhea.
Joe: I thought I was gonna have a nice shit at first but then I ended up obliterating the toilet bowl.

Gabe: Yeah, that's what you call the poop cap.
by Andy Stafford September 23, 2015
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