My Abundant Butt (お尻ドッサリ - Oshiri Dossari) is Hibari's Aerial Secret Ninja Art in Senran Kagura Burst. It requires one bar of Ninja Art Energy to use and for Hibari to be in the air. Hibari becomes able to use it after getting to level 15.
While in the air, Hibari uses her ability to make herself several times larger. Then she simply allows herself to fall to the ground on her back, smashing the opponent(s) around her with her posterior.
Hibari's "Butt Go Boom!" appears to be derived from this attack.