Yes, whomp is in the scrabble dictionary.

What is the definition of womp?

: an abrupt increase in the illumination of a television screen resulting from an abrupt increase in signal strength.

Is womp a real word?

It's a noun with numerous slang definitions and everyday uses. You might use it to refer to the sound that a dinosaur makes when it sneezes, or that a bass makes when it's dropped (thanks, Urban Dictionary).