Noun. A bottom that is clearly disproportional to the rest of the person's torso and legs. However it only refers to bottoms that are greater in size and not smaller. If the person fell down on their bottom then the large bottom would provide more than enough padding to prevent serious injury. The term "boom boom" originates from the phrase "baby went boom boom on their bottom."
Look at him, he has a boom boom bottom.
by evanwhitelightning September 15, 2008