It is your "gooch" or "taint" after weeks of not showering. It becomes a greyish color due to the lint build-up and hardens due to accumulation of crusty sweat. It becomes very itchy and bares a striking resemblence to Destro, villian from G.I. Joe. Nothing is smellier or is more of a nusance to any G.I. Joe on the job, then your sweaty taint in the summertime.
Fuck. My grey grundels actin' up. It's crustier than my girlfriend's asshole after a week long cream pie.
My girlfriend just ate out my grey grundel and she looks like she just ate the icing off of a Destro themed birthday cake.