Defined as the "Jack" in a deck of cards. Often used during high stakes Poker Hands (Texas Hold 'em, Pineapple poker, etc.). Most commonly used when a player has a pocket pair of Jacks, the 4th best hand in Poker.
"Can't believe you won that big pot, were you bluffing?" "No", says Ezekiel "I had pocket Jizzops and hit 3 of a kind".