Hiccups are involuntary contractions of the muscle tissue between the chest cavity and the abdominal cavity known as the diaphragm. This spasm of the diaphragm causes an intake of breath and simultaneously the vocal cords in the throat close causing the characteristic sound of a hiccup. Typically this spasm repeats every few seconds and last for a few minutes. Rarely they can continue for days or longer and become a situation requiring professional help.
Hiccups can be caused by eating or drinking too much, a sudden cold or hot drink, swallowing air or some type of emotional excitement or stress.
[search helps: hiccough, synchronous diaphragmatic flutter (SDF), singultus]