疲乏 is a compound noun meaning 'tiredness' or 'exhaustion' — a physical or mental state of depleted energy. The first character 疲 (pí) means 'weary' or 'fatigued', often implying prolonged effort; the second 乏 (fá) means 'lacking' or 'insufficient', reinforcing the sense of depletion. Together, they form a formal, slightly literary term that emphasizes deep or sustained weariness — more intense than just feeling 'tired' (累). It’s commonly used in medical contexts, health discussions, and written reports.

Unlike colloquial terms like 累 or 困, 疲乏 carries a clinical or descriptive tone and appears frequently in doctor-patient communication, health articles, or official wellness guidelines. It rarely functions as a verb or adjective on its own and almost always appears as a standalone noun or after modifiers like 感到, 出现, or 严重. It does not take aspect markers (e.g., 了, 过) directly and is seldom used in casual speech among friends.