1 to put on special clothes, especially in order to look like sb/sth else 打扮成…: The children decided to dress up as pirates. 孩子们决定扮成海盗。

2 to put on formal clothes, usually for a special occasion 穿上礼服: You don't need to dress up for the party. 你用不着穿礼服去参加这次聚会。