Whatever you want it to mean. It can be used in place of verbs, adjectives, nouns, whatever. That is the glory of the booyah. Booyah can also be used as a sort of insult (refer to example 3). You can also add to it to make it even more awesome!
I just booyahed that booyah!-or-I would totally booyah her!
Kid1: "BOOYAH!"
Kid2: "BAM FLIP BOOYAH!"
Bam flip booyah would be a counter-booyah and therefore kid1 would have one-up kid2's counter or be humiliated.
An incredibly intense drinking game said to have originated in central Canada. It requires 4 dice and a Booyah Bible, and stats are recorded for all eternity. Do not attempt to play unless you are a seasoned drinker.