Used as an exclamation when something incredibly spectacular happens. It can also be used to describe a clutch performance or an otherwise impressive feat.
As his teammate clinches a victory, Jake exclaims “Boom Baby!!”
When something 'extra' special happens, just add "Kaboom" for emphasis...
1.(n). A weapon first deployed by the United States during WWI which involved strapping high-explosives to infants and dropping them from planes into trenches.
2.(n). In WWII, the Baby Boom was America's equivalent to Hitler's Blitzkrieg, although much less effective.