When the person receiving a blumpkin drops a huge turd and the person giving the blumpkin gets a huge splash of shit water on the underside of their chin; When the person giving a blumpkin gets water splashed on their face from a dropping or exploding shit.
Kerplunk + Blumpkin = Kerblumpkin
I need to wash this shit water off my face because my boyfriend gave me a gnarly kerblumpkin.
true love, getting a blowjob while on the toilette
my g/f gave me a kerblumpkin yesterday!