lah-di-dah

• la-di-da, lah-de-dah, la-de-da
• lardy-dardy (archaic)

c. 1880s, with a comeback in the 1980s due to its use in Annie Hall (1977) by Woody Allen, although in a different context, spoke by the actress Diane Keaton.[1][2]

• IPA^(key): /ˌlɑːdiːˈdɑː/

• Audio (US)

  (file)

• Rhymes: -ɑː

lah-di-dah (comparative more lah-di-dah, superlative most lah-di-dah)

1. (British, derogatory) Of or from the upper class of society.
2. (British, 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.

The adjectival usage is not common in the US.

lah-di-dah

1. (mildly derogatory) Expression of disdain for pretension or haughtiness.

   Well, lah-di-dah, mister Park Avenue manicure.

2. (US) Not a care in the world. (used in a sing-song voice, for childhood rhymes)