A belly buster is a one-card inside straight draw.
Explanation. Also called an inside straight draw or gutshot, a belly buster occurs when you have four cards to a straight but missing one in the middle (e.g. holding 5‑6‑8‑9, needing a 7). It’s less likely than an open-ended draw, but still playable in certain situations—especially when priced well or used with fold equity. New players learn to recognize its low probability and calculate implied pot odds before committing chips.