An ABC player is somebody who plays solid starting hands and is usually predictable. In Holdem, the player might only play AA, KK, QQ, AK, and AJ. In Omaha Hi low, he might only play A234, A23K, AA23, A2KQ, and A235. Also can mean that you hold A23 in high-low or lowball games.
A Las Vegas term used to describe the first three dealt cards in Seven Card Stud and its variants when they are ace, duece and trey. Also a player who never changes his game, always plays the same way....he pays it ABC