Simply put it is the male equivalent of a woman's camel toe. Usually caused by the seam of tight but thin leg wear such as spandex, the testicles and penis form two bulges on opposite sides of the seem that vaguely resembles the hoof, or "knuckle" of a moose. hence "Moose-knuckle"
Jon didn't wear underwear under his skintight Peterpan costume, and everyone could see that he had a moose-knuckle.
de ChicagoBrian 15 juin 2011