Not having enough people working to do the job properly. If a ship, a factory, a hospital ward, an office or a shop is undermanned, there are simply not enough bodies there — so the work is slow, things get missed, and the people who are there are worn out. Note that it describes the PLACE or the OPERATION, not the person: the hospital is undermanned, the nurses are overworked. It began as a sailing word — a ship needed a certain number of hands to sail it safely — and it still feels a bit heavier and more official than the everyday way of saying it, so you meet it most in news reports, complaints to management, and safety reports. In ordinary speech people are more likely to say 'short-staffed' or 'we're short today'. Two things to know about the word itself. First, 'man' inside it is the old sense of 'man' meaning 'to work at, to supply with people' — the same 'man' as in 'man the phones'. Second, because of that, many people now feel the word is dated or male-sounding, and newspapers and companies increasingly write 'understaffed' or 'short-staffed' instead. Both are safe; 'undermanned' is not wrong, but it is the older-feeling choice, and you will hear it from older speakers and in military or shipping contexts more than from a young manager. There is no common verb 'to undermann' — the word is essentially only used as an adjective, usually after 'be': the department IS undermanned.

人手不足的、缺人手的（台灣一般說「人力不足」「缺人」；注意是形容單位或工作，不是形容人）