down是什么意思 a. 向下的adv. 下, 下去, 降下prep. 往下, 沿着n. 丘陵, 软毛, 开阔的高地[计] 向下, 退下命令 n. soft fine feathersn. (American football) a complete play to advance the footballn. English physician who first described Down's syndrome (1828-1896)...