The term Backdoor refers to a hand requiring consecutive cards on the turn and river to become a strong made hand. Also known as “runner-runner”.
Example: If you’re holding K♥ J♥ on a flop of A♣ 7♥ 2♠, you have a backdoor flush draw because two consecutive hearts on the turn and river would give you a flush. You also have a backdoor straight draw, as you could hit two consecutive cards (a queen and a ten) to make a straight.