A hiccup is a spasmodic contraction of your diaphragm. (Your diaphragm, in turn, is a thin muscular wall between your stomach and your lungs.) They usually occur at regular intervals, too. Sometimes it helps if you intentionally tighten your diaphragm just before the next hiccup is due, and keep it tightened while the spasmodic contraction tries to make you hiccup. Repeat. I can usually cure mine after two or three hiccup cycles. To tighten your diaphragm (I know this is a gross way of expressing it, and I apologize) bear down, like you were trying to poop.