To hide drugs in the crotch of your pants so that if a police dog catches the scent, it will look as though he's just sniffing your crotch the way dogs often do.
(verb) to grip or hold something with the inner thighs while sitting in order to leave one's hands free. This is almost always done in a vehicle with a fast food item, such as a beverage or carton of fries.
We're out of cup holders; looks like I'll have to crotch my root beer.