Onimonapia (meaning word that is spelled like a sound) that is supposed to stand for 70's guitar Porn-riff. Usually this is the music that came on when the action was just about to get started. It has been used in a subcultural context to denote any porn-like or pornified situation.
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.
Your friend picks up an extra large sausage. This is a great time to sing Bom Chicka Wah Wah.
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.