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