Being a sound, it could also be spelled several different ways such as: Bow Chicka Bow Wow, Bow Chicka Wow Wow, Wakka Chikka Wakka Chikka, etc.
You see a hot guy/girl that you could imagine yourself in a porn with. Also a good time to sing Bom Chicka Wah Wah.
Some examples of the Bom Chicka Wah Wah porn music riff being sang in pop culture include it being used as the catchphrase sang by a hot girl for axe/lynx advertisements, tucker in machinema series red vs. blue, and stuey from the TV show the family guy, and character 'rachael' from TV show friends.
Woman: Bomchickawahwah! Chicka ow chicka wah wooooooooow!