1. A term for a "stroke", a cerebrovascular accident (CVA), often associated with loss of consciousness and paralysis of various parts of the body.
2. Sudden impairment of neurological function, especially that resulting from a cerebral hemorrhage; a stroke.
3. Any acute clinical event, related to impairment of cerebral circulation, which lasts longer then twenty-four hours; brain attack.
4. A sudden effusion of blood into an organ or tissue.
5. A fit of extreme anger; rage.
6. Etymology: apoplexy comes from the Greek apoplexia, "a seizure", in the sense of being struck down.

In Greek plexe is "a stroke". The ancients believed that anyone suffering a stroke; or any sudden incapacity, had been struck down by the gods.

A "sudden fit of paralysis and dizziness", from Old French apoplexie or directly from Late Latin apoplexia; from apo-, "off" + plessein, "hit".