[n] 降落,秋季,落下,跌落,瀑布,陷落
[v] 降下,砍倒,落下,陷落,跌倒,下垂
[adj] 秋天的
fall about laughing [v] 禁不住大笑起来
fall about with laughter [v] 禁不住大笑起来