the fact of something suddenly collapsing (突然的)塌陷,坍塌,倒塌 The cave-in at the mine was caused by a sudden rush of water. 矿井坍塌是由突然的水流造成的。
the act of finally doing what somebody wants after you have been opposing them (突然的)塌陷,坍塌,倒塌 This cave-in looks weak and pathetic from such a clever politician. 从一个如此聪明的政治家的角度来看,这种让步显得软弱和可悲。