When somebody is in a really bad mood, somebody might have urinated into his bowl of cereal earlier.
by elwood_j_blues August 01, 2006
Hey man I don't mean to "piss in your Cheerios" but I saw your lady blowing some guy in the parking lot at bar close last night.
by Bigbadbamf February 17, 2014
"Sorry to have pissed in your Cheerios, but that chick that just gave you a blowjob has an Adam's apple and a hard-on."
by Funk knuckle August 01, 2014