A blind bet is a wager placed without looking at your own cards. A poker player who has been folding for a while might decide to join the next hand blind, or to check or call “in the dark” before seeing the flop. It speeds up play, can unsettle opponents and is sometimes part of a bluff.
A bet made blind still counts in full. Once the chips are in the pot, the decision cannot be taken back after the player looks at the cards.
The phrase overlaps with the compulsory blinds — the small and big blind — that two players post before the deal in games like Texas Hold’em. Those are forced, whereas a voluntary blind bet is a choice. Some casino poker games played against the house also have a separate betting spot labelled “Blind”, with its own paytable.