A harbanje is the first dump of the morning after a heavy night's drinking. Don't pretend that you don't know how satisfying that first
crap of the day is. Your body, after hours of
heavy-duty punishment, bad dancing and disturbed
sleep, is making its first attempt to kick out all
the shit (quite literally) that you've filled it with. Once it's plopped out, you feel at least 3000% better, at last ready to face the world outside with a respectable (yet not excessive) amount of
fresh-faced enthusiasm.
Please note that, while harbanje can be used in many of the contexts associated with its everyday cousin, the shit, it is not quite as versatile: it is merely a noun and cannot be used as a verb or an adjective. There is much possibility for incorrect usage.