An involuntary spasmodic contraction of the diaphragm, causing a beginning inspiration that is suddenly checked by closure of the glottis, causing a characteristic sound.

Some medical researchers believe that people hiccup because their bodies are trying to push out air that is trapped between the gulped-down food in full stomachs; or, perhaps their bodies are trying to protect them from choking, by preventing them from eating while they are so full.

Another explanation for hiccoughing may be the result of eating or drinking too much, too quickly, and these may confuse the coordination between the breathing and swallowing processes and so irritate the diaphragm.