la-di-da
A loud, fake sound you make when you think you're better than everyone else.
La-di-da! I just got a 100 on my math test. You got a 99. That's not even close.
He yelled 'la-di-da' when I showed up in a shirt he thought was 'basic.'
She said 'la-di-da' after I told her I beat her in a video game.