She tried to pass off she was a doctor, but got exposed quickly.

pass off 是由动词 pass 和副词 off 组成的短语动词。pass 本意是"通过、传递"，off 表示"离开、脱离"。 pass off 在这里的意思是"冒充、假装"，指试图让别人错误地相信某事物或身份是真实的。