What is "hyperpyrexia"

Hyperpyrexia \Hy`per*py*rex"i*a\, n. [NL. See Hyper-, and Pyrexia.] (Med.) A condition of excessive fever; an elevation of temperature in a disease, in excess of the limit usually observed in that disease.

n. (context medicine English) An excessive and unusual elevation of set body temperature greater than or equal to 41°C (105.8°F), or extremely high fever.

n. extremely high fever (especially in children)