A dead hand in poker is a foul hand that can’t participate in the game due to some kind of infraction. The player whose hand is declared dead is automatically disqualified from the hand.
Dead Hand Poker Example:
Let’s say that you are facing a big raise, and you take a couple of minutes to think through your decision. After some time, someone calls the clock on you. If this happens, you will have to decide before the predetermined amount of time runs out, or else your hand will be declared dead.