If I said "I have other fish to fry" after being asked to do something, would it certainly sound rude? Would it depend on my intonation? I'm not sure whether this answer would suggest that the other person was asking me something unimportant....
It'd sounds brusque - rude, in the wrong company. You could probably get away with it if you were talking to a friend, but otherwise don't take the risk. It's more commonly used in the 3rd person: nobody's nose will be 'put out of joint' if you say that someone else has something better to do.
Last edited by BobK; 25-Feb-2012 at 18:25. Reason: Link added