A side agreement when someone is all-in for a player in a pot to put up money that guarantees a payoff of a set amount in case the opponent wins the pot. The bet may be between the players involved in the all-in, or can also be between a player in the hand and another not in the hand.

"Taking insurance" is different from "running it twice" (or more), but a similar principle is involved in that it is action made apart from the actual hand designed to reduce variance. While common in blackjack, insurance doesn't come up that often in poker.