Of or from the upper class of society.
Affecting upper-class or superior airs.
She was all la-di-da, with her nose in the air, and we were all struggling not to laugh because that would be gauche.
(mildly) Expression of disdain for pretension or haughtiness.
Well la-di-da, aren't you the impressive personage, with a feather in your hair yet.
Not a care in the world (used in a sing-song voice, for childhood rhymes)