The rare situation whereby a drawing poker hand has two inside straight draws. For example, in a Texas Holdem poker game where a poker player holds 4-9 and the flop is 5-6-7. Either a 5 or an 8 would fill an inside straight draw.
A special kind of open-ended straight, for example the board shows 5-6-8 and you hold 2-4. You can hit your straight by catching two cards, a Three or a Seven. More valuable than a regular open-ended straight because of it's deceptive qualities.
An open-ended straight draw where two different cards will make your straight, but each card is higher than your lowest card and lower than your highest card. For example, if you have 6-7 and the flop is 4-8-10, you have a double belly buster straight draw because either a 5 or a 9 will complete your straight.
When a player has two inside straight draws, effectively giving them the same chance of making a straight as having an open-ended straight draw. For example, if a player has K-7 and the board is showing 6-9-T-Q, then either an 8 or a J will give a straight.
A hand with 2 inside straight draws. An example might be a flop containing 10-8-6, when you have 7-4-a 9 or a 5 will make the hand into a straight. The odds for getting the straight from a double belly buster are the same as for an open-ended straight draw.