get dressed' 只是指穿衣服,把衣服穿好的意思.
"dress up' 有'打扮'的意思,不一定是要打扮得漂亮,只是表示特殊穿着的意思.例句如下:
1.(早上起床) We're late.Please get dressed as fast as you can.我们晚了,快穿衣服/快把衣服穿好.
2.The party was canceled.I got dressed up for nothing.聚会取消了,我白打扮了.
3.I want to dress up as a duck this Halloween.今年万圣节我要装扮成一只鸭子(的样子).
这样清楚了吗?