In games with blinds, a straddle is an extra blind that the player immediately to the left of the big blind pays of his own accord. It must be at least two big blinds.
The player who pays the straddle is the new big blind in the first betting round and may finish it. He therefore recieves an improvement in position since his opponents must act before him. A straddle counts as a blind and not a bet, so the player who made it can still raise if everybody calls his straddle.
Straddles are used to increase the wagers in around and to put more money and action into the game.