Big Dog
Big dog means an underdog, and in some home games a nonstandard hand of nine to ace with no pair.
The simple explanation
Big dog has two meanings. In general it is an underdog, someone with a very low chance of winning. In some home games it is also the name of a special hand: five unpaired cards from the nine to the ace. Special hands like this are not part of regular poker.
A closer look
As a hand, the big dog ranks below a little tiger and above a little dog in games that use these rankings. The whole family of hands, such as tiger and cat and dog, belongs to home-game rules and varies from group to group. In ordinary poker an unpaired hand like 9-J-Q-K-A is just a high-card hand.
A practical example
A home game with special rankings shows 9♦ J♣ Q♥ K♠ A♦, five unpaired cards from nine to ace, and calls it a big dog.
Full explanation
Big dog means an underdog, and in some home games a nonstandard hand of nine to ace with no pair.
Big dog is slang for an underdog: the person who has a very low chance of winning. It is used in sentences like ‘he was the big dog in that hand’.
In some private games the word also names a nonstandard hand of five cards from nine to ace with no pair. It ranks below a little tiger and above a little dog.
These named hands are not in the standard ranking. They exist only where the players agree to use them, and the ranking can differ between groups.
If you meet a special hand in a home game, ask where it ranks before you bet on it.