mad yeahs
a way of showing you're completely relaxed and also super proud of something that was absolutely awesome.
I got a new phone and said, 'Mad yeahs!' and then took 500 selfies.
When my friend won the race, I said, 'Mad yeahs!' and then ate a whole cake.
After I beat my brother at chess, I said, 'Mad yeahs!' and then bragged for an hour.