Definition of underdog
In poker or any other competition, the underdog is the underdog. There is the favorite on the one hand, the one who has the best chance of winning the game, and on the other hand, the one who will win the game in a smaller proportion of the time. The underdog can be a big underdog, i.e. his chances of winning are very low, or a small underdog, i.e. his chances of winning are a little lower than the favorite, but still interesting.
The underdog in poker
In poker, a player can be called an underdog or a poker hand can be called an underdog. If there is a heads-up duel between two players, the better of the two players will be called the favorite while the other will be the underdog. In terms of poker hands, if two players are all in in a hand and one has QQ and the other has AA, QQ is said to be underdog. Underdog does not mean that we never win, but that we are not favored to win.