fall down意思如下：
1.掉下,落下,跌倒,价格下跌：The old lady fell down in the street and broke her leg.老妇跌倒在大街上,摔坏了腿.The price is falling down every day.价格每天都在下跌
2.拜倒,跪倒：They fell down before him.他们拜倒在他面前.
3.倒塌：The old house soon fell down.这座老房很快就倒塌了.
4.毫无结果,(在…方面)失败(常与on,in连用),被表明为不正确、不足或不妥,证明是不令人满意的(或不切合实际)：Your plan fell down when it proved too costly.你的计划是不切合实际的,因为它被证实耗资太大.
5.漂流而下
而 fallen down 中的fallen 是 fall 的过去分词
不明白的再问哟,请及时采纳,多谢!……sorry。没看见。多谢啦。You are welcome.