I think it means communal bed, but some people are saying it means collective bed, which doesn't make any sense. Also, google translate believes it isn't a word, so is it not used anymore?
大 - big
通 - communal/ connect
铺 - 床铺 - bed/ 铺位 - bunk
通 = connect (one bed next to another like connected, therefore called 通铺) or 通 = 通用 (beds are communal therefore called 通铺)
大通铺 refers to a hostel (旅馆) or dorm (宿舍) that features communal beds (cheap, no privacy),
It can be translated as 'communal beds hostels' (大通铺旅馆) or 'communal beds dorm' (大通铺宿舍)