bottomless pit
noun [ C usually singular ] uk/ˌbɒt.əm.ləs ˈpɪt/ us/ˌbɑː.t̬əm.ləs ˈpɪt/
无底洞；无休止的情形
something that seems to have no limits, or a situation that will never end
We'll be pouring money into a bottomless pit if we try to keep that factory open. 如果继续让那个工厂运转下去，我们无异于把钱投入无底洞。