Well la-di-da, aren't you the impressive personage, with a feather in your hair yet..
disapproval If you describe someone as la-di-da, you mean that they have an upper-class way of behaving, which you think seems unnatural and is only done to impress people. I wouldn't trust them in spite of all their la-di-da manners. used to describe someone's behaviour when you think they are talking and behaving as if they consider themselves better than other people = snobbish (Copying the speech of upper-class people)