In texas hold em poker terms it means pocket Kings (2 kings). A king (any suit) is often called a cowboy and as we all know in the movie "Broke Back Mountain" two cowboys were together hence the poker name for pocket kings or two cowboys together.
If someone has a pocket ace and king its called a "Cowboy with a Bullet". If you have pocket or 2 kings, a better hand, then you would have "Broke Back Mountain".
In the poker variant of Texas Hold 'em, The "Big Lick" refers to holding a six and a nine as your two hole cards. In sexual terms, when a man and a woman, two women, or I guess two guys are performing oral sex on one another at the same time, this is referred to as a "69". As with the "Big Slick", the "Big Lick" often produces fortunes to be lost when gambling.
In gambling, if someone, hopefully a woman, has a 6 & 9 in their hand then you would say they have the "big Lick". Even better is if someone has pocket 6 & 9 and they pair up with a 6 & 9 on the table (flop, turn, or river) then that is called a "Poker Orgy".