Fallen.法尔fallv.落下；倒下；来临n.秋天；落下；瀑布fall off rate下降速率falling-offn.下降；减退fallen leaves落叶fall on board撞着; 攻击faller roller针板罗拉falling chain落链fallen column陷落柱falling speed下降速度,下落速度falling wedge伐木楔fall velocity沉降速度