Hiccups is just one example of a myoclonic jerk, which is a brief, involuntary twitching of any muscle or group of muscles. In the case of hiccups, the muscle in question is (as you probably know) the diaphragm.
In horses, where it usually has a more serious underlying cause than in humans, hiccups is known as synchronous diaphragmatic flutter (SDF) or 'thumps'.
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