What does bwah-chicka-bwah-bwah mean?

bwah-chicka-bwah-bwah meaning in Urban Dictionary

an imitation regarding the music that underscores adult movie. Initially utilized as an introduction in IRC rooms and bulletin panels, it's evolved to incorporate the actual act of sexual activity. The expression initially included, "*ding dong*", "Pizza Delivery", and "bwah-chicka-bwah-bwah" (in that purchase) as a representation of exactly how a typical low-budget person film would begin. It had been later on reduced to simply "bwah-chicka-bwah-bwah".