heatstroke(n = noun.state) heat hyperpyrexia - collapse caused by exposure to excessive heat;
is a kind of collapse, prostration
has particulars: heat exhaustion, heat prostration, insolation, siriasis, sunstroke, thermic fever

   A physiological disturbance caused by exposure to excessive heat, resulting in rapid pulse, hot dry skin, and fever, leading to loss of consciousness. [WordNet 1.5]

heatstroke, n. a feverish condition caused by excessive exposure to high temperature.