Straddle

1. To bet an amount that is typically double the size of the big blind before cards are dealt. The blind raiser then has the final option to raise preflop.
2. A blind bet that is typically twice the size of the big blind made by the player under the gun before cards are dealt, as in "live straddle" (noun).

Example

In a $10/20 No-Limit game, the player in the one-hole puts up a live straddle of $40. Everyone calls the $40 bet, and then the straddler would have the option to check and see a flop, or to raise.