A timeserver is someone who does just enough at work to get by and no more — putting in the hours, waiting for the day to end, the pay to arrive, the pension to come. It is an insult, and a fairly cutting one, because it says the person has no real interest in the job, only in surviving it. The word is old-fashioned and formal now; you are far more likely to meet it in a novel or a serious newspaper than in speech, where people would say something like 'he's just putting in time' or 'she's coasting'. There is an older and slightly different sense you may still run into in reading: a timeserver as someone who changes their opinions to suit whoever is in power at the moment — a person who serves the times rather than any principle. That sense is closer to the original one, and the lazy-worker meaning grew out of it. Both are disapproving. It is written timeserver or time-server; both are fine.

混日子的人；尸位素餐者（帶明顯貶意，指上班只等下班、只求安穩的人；書面語，口語很少用）