Nosing around the grundle area -- usually performed by a dog trying to get your attention (aka crotch-sniffing) or another person REALLY trying to get your attention.
"Dude, get your dogoff of me!"
"Oh, sorry man. Spike! No grundling the guests!"
The act of taking your strong arm and feeding it under an unsuspecting friend's legs as he stands and lifting him up by his grundle. This will cause extreme pain of the marble sack and or loss of baby makin mojo.
When someone pisses and shits with their dick shoved up their ass- creating a violent ricochet splatter effect with the feces and urine splashingeverywhere.
"Pipushka was grundling so hard that the guys could hear the feces and urine splattering against the inside of her trousers as he was patiently waiting in the queue."
"Mekmat always looked up to the OGs for pointers and advice towards grundling. He could never keep his dick shoved up his own ass once he began shitting and pissing, his dick would just pop out and start pissing everywhere as free form feces sprayed out of his ass"