A butterfly is an inversion found exclusively on two Vekoma roller coasters. A butterfly begins like a normal loop, but as the track goes up it twists 45 degrees to one side or the other, and then when it is headed down the track twists back. The maneuver is then repeated but in reverse. It is similar to a batwing, however the coaster exits the element traveling in the same direction as it began.
Two roller coasters, both from Vekoma, have a butterfly element: