Pyrexias, also known as fever, is an elevation in body temperature above the normal range. Antonyms for the word "pyrexias" would be words describing conditions where the body temperature is lower than normal. For example, hypothermia is a medical term for abnormally low body temperature. Other antonyms could include terms such as chill, coldness, or frostbite. These conditions can occur due to exposure to cold weather, cold water, or prolonged exposure to air conditioning. While pyrexias can indicate an underlying health problem, such as an infection or inflammation, hypothermia can be life-threatening if not treated promptly.