How would you define it?
In poker, it does not necessarily mean dead literally. Dead money simply means the amount of money placed in the pot other than the equal amounts bet by the remaining active players.
For those who have folded, the money they have contributed is considered to be dead money. On the other hand, there’s also a thing like a dead blind which is a blind posted by a player returning to a game after missing the blinds or an odd chip left in the pot from a previous deal.
Pot odds of plays are very much affected by the amount of dead money or the rules that are based on the number of players. A good example for this is many Omaha players use the common rule of thumb that states one should raise with a nut low hand on the last round only if there are four players in the pot and just call if there are only three. However, if there is a considerable amount of dead money in the pot, this changes the odds to favor raising bets, even with only three players.
At times, the term dead money is used in a derogatory sense to refer to the money that has been placed in the pot by the players who are still legally allowed to win it but who are unlikely to do so because they are quite lacking on the skills needed, increasing the expected return of the other players. This is of course applied to the player himself as well.
Dead money is also a term for a player who is rather unskilled or a person who has less chance of winning.
Using dead money in a sentence:
“Let’s invite him every week because he’s dead money.”
Dead money has several meanings but it is quite easy to get and understand.