The larger version of
boom.
Boom is just a "boom" while
KAboom refers to the "WOW" effect
verison of boom. Something truly boom, becomes
kaboom.
Can sometimes be written with multiple "o"'s such as: kabooooooom.
Meaning an even larger boom than kaboom.
Usually said with a special voice or sounds. Putting weight on the "o"s.
ps: if you actually say this, you might be considered a retard as it sounds pretty stupid saying this.
Also an onomatopoeia of a huge explosion