cave in
  倒塌,坍塌,凹進,下沈;屈服,認輸
  cave in
       n : the sudden collapse of something into a hollow beneath it
           [syn: subsidence]
       v : break down, literally or metaphorically; "The wall
           collapsed"; "The business collapsed"; "The dam broke";
           "The roof collapsed"; "The wall gave in"; "The roof
           finally gave under the weight of the ice" [syn: collapse,
            fall in, give, give way, break, founder]