The residual ejaculate gathered under the foreskin of the penis before the guy has a chance to shower or clean it away or residual ejaculate left behind by a man whose hygeine habits aren't good, maybe hours or days old.
Oh MAN! I ain't suckin' that sleazy thing baby! Y'all got some old head-cheese left under there!
head-cheese is duck-butter -- a waxy combination of cum, piss, sweat, and dead dick-head cells that can accumulate under an uncircumcised guy's foreskin on his corona.
I sucked off this uncut cadet's dick -- he tasted good - even his head-cheese!