Gutshot

An inside straight draw — you hold four of the five ranks you need with a gap in the middle, so only one rank completes it. Holding nine-ten on a board of seven-eight-king, any jack makes the straight.

Four outs: about 17% from the flop with two cards to come, and about 9% on the turn. Roughly half as likely as an open-ended draw.

Rarely on its own — the odds are too thin to call large bets. It becomes playable when combined with other equity (a pair, an overcard or a backdoor flush draw) or as a semi-bluff where the fold equity, not the draw, pays for the bet.