The Collaborative International Dictionary of English v.0.48:
Pyrexia \Py*rex"i*a\, n.; pl. Pyrexi[ae]. [NL., fr. Gr. ? to be feverish, akin to ? fever.] (Med.) The febrile condition. [1913 Webster] PyrexialWordNet (r) 3.0 (2006):
pyrexia n 1: a rise in the temperature of the body; frequently a symptom of infection [syn: fever, febrility, febricity, pyrexia, feverishness]