精疲力竭 is an idiomatic four-character adjective meaning 'completely exhausted'—physically, mentally, or emotionally. Literally, it breaks down as 精 (jīng, 'vital spirit' or 'mental energy'), 疲 (pí, 'tired' or 'fatigued'), 力 (lì, 'physical strength'), and 竭 (jié, 'exhausted' or 'depleted'). Together, they convey total depletion of both inner vitality and outward stamina—a state beyond ordinary tiredness.

This expression is commonly used in formal writing, literature, news reports, and serious spoken contexts to emphasize extreme exhaustion after prolonged effort, intense stress, or demanding physical activity. It carries a slightly literary tone and is stronger than everyday terms like 累 (lèi) or 疲劳 (píláo). While not slang, it’s widely understood and frequently appears in descriptions of athletes, caregivers, disaster responders, or students pulling all-nighters before major exams.