a term that means totally awesome. like unbelievably, completely, stupendously, amazing!! when something is so cool, cool just doesn't cut it. it can also include a fist pound or high-five with it.
Bob: I just won 1,000,000,000 dollars in the lottery!!!
John: BOOMSHAKALAKA BOOYAKASHA!!!!!!
Perry: I just totally nailed that that smokin, blonde chick.
Turk: Boomshakalaka Booyakasha!! YA NO WAT IM SAYIN!?!?!
Booyakasha is a polite way of saying booya.
It comes from hebrew בְּבַקָּשָׁה (b'vakashá) which means "please" or "you're welcome" and from booya (see booya)
Sasha Baron Cohen probably invented it for his character Ali G.