A butterfly twist or b-twist is a tricking movement, originating in martial arts such as Wushu. It consists of a 360° twist in the air while the body is kept horizontal.
It is necessary to have a high, clean butterfly kick before this move can be learned. Some consider an aerial to be a good progression towards a butterfly twist, whereas as others consider a butterfly kick to be a progression towards an aerial. You should also be able to spin 360 degrees vertically in the air.