1. lah-di-dah - Adjective
2. lah-di-dah - Interjection
(Britain, derogatory) Of or from the upper class of society.
(Britain, derogatory) Affecting upper-class or superior airs.
Synonyms: pretentious, snooty; see also Thesaurus:arrogant
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 derogatory) Expression of disdain for pretension or haughtiness.
Well, lah-di-dah, mister Park Avenue manicure.
(US) Not a care in the world. (used in a sing-song voice, for childhood rhymes)
Source: en.wiktionary.org