A gymslip is a school dress with no sleeves. Girls in Britain used to wear it over a shirt, as part of school uniform. It hangs from the shoulders and often has a belt at the waist, a bit like an apron that grew into a dress. The name has gym in it, though actually girls wore it all day in class, not only for sport — it began as clothes you could move in, then became ordinary uniform. You almost never see it now, except in old photographs, stories about old schools, or a few very traditional places. It is a British word. American English is more likely to say pinafore or jumper for a similar dress.

背心裙（舊式英國女學生校服）