Colic
Abdominal pain in a horse. Not one illness but a whole range of them, from mild to fatal, which is why it is always taken seriously.
Colic is a symptom that has been treated as a diagnosis for so long that it functions as one. The word covers any condition causing abdominal pain, and those conditions vary enormously in both cause and severity — which is the reason nobody sensible waits to see whether this one is the mild kind. The signs are worth learning by heart: pawing repeatedly with a front foot, looking round at the flank, curling the upper lip, kicking at the belly, lying down and rolling from side to side, sweating, standing stretched out as if to urinate, and passing less dung than usual. A horse doing any of that gets a phone call to the vet, not an hour of watching.
Sources
See also