In poker, a dominating hand is one with an overwhelming statistical advantage over another specific hand. For example, in Seven-card stud, while a Starting hand of K? K? Q? has the lead over A? K? 10?, the latter has many outs (ways to improve) to beat the former (catching an ace, the straight, the flush, etc.), making it a roughly even contest. However, the first hand dominates in a contest with a hand like Q? Q? J?, because this hand has no ways to improve that the first one doesn't also have (two pair, trips, straight), and the first hand has some of the second hand's outs as well (unseen cards include two kings, but only one queen), giving it a significant advantage.
This concept is most important in no limit play, where it is possible to bet all your money early in the hand. One must judge not only whether your opponent's hand might be better than yours, but whether or not it might dominate yours to such a degree that long-run fluctuations of luck will amplify the consequences of a mistaken play rather than mitigating them.

One of the things that makes no limit Texas hold 'em strategically rich and interesting is the unusual relationship of advantage and dominance among various Starting hands. For example, the hand A? K? is a slight favorite over J? 10?; this hand is a slight favorite over 4? 4?; and in a non-transitive relationship, the fours are a small favorite over A? K?. None of these hands dominates any other, but A? K? does dominate A? Q?, 4? 4? is dominated by 7? 7?, and J? 10? is dominated by Q? J?.

http://www.gamblingweblog.com/2008/11/06/dominating-hand-2/