| Noun | 1. | heat hyperpyrexia - collapse caused by exposure to excessive heatcollapse, prostration - an abrupt failure of function or complete physical exhaustion; "the commander's prostration demoralized his men" heat exhaustion, heat prostration - a condition marked by dizziness and nausea and weakness caused by depletion of body fluids and electrolytes insolation, siriasis, sunstroke, thermic fever - sudden prostration due to exposure to the sun or excessive heat |