exhaustion; extreme fatigue
A rare, literary noun for deep physical or mental exhaustion. In modern Japanese, 疲労 (ひろう) or 疲れ (つかれ) are far more common.
In old texts, 疲憊 is used as a word expressing extreme fatigue.
heat exhaustion
A Sino-Japanese compound of 疲 (hi, 'tiredness') and 憊 (hai, 'exhaustion'). The exact historical derivation is uncertain; the spelling is conventionally associated with extreme fatigue.