A foomp is when something magical happens along the lines of something growing instantly or blowing up instantly but in a pleasant way. More along the lines of something good just happened.
a gun goes bang.
fireworks go bang.
cars crashing go bang.
an instant growing mushroom tree goes foomp.
a penis goes foomp.
a scoreboard goes foomp.
The sound that occurs when certain items accidentally hit the floor, your head, or while opening a champagne bottle. Foomp can also describe something exaggerated or tall.
Dude, I knew instantly that a soccer ball just hit you in the head because I heard it go foomp!
Whoa, did you see that blonde chick's 80s waterfall bangs? They were all foomp!