down在羽绒服里是羽绒的意思。例如duck down，“鸭的绒毛”，即“鸭绒”。例句：A down coat is an insulated winter coat that is filled with fine feathers from a duck or goose. “羽绒服”是一种隔绝寒冷的（insulated）冬衣，里面填充了羽绒（fine feathers）。