From a Whip position, pull towards the bar, let go, open your legs and grab the bar between your legs as you leg your legs drop down. This trick can be performed while going backwards or (more rarely) while going forwards. It can also be performed in the catcher's arms and is a move often seen in a doubles trapeze act or cradle act.
You can find out more about this trick in my books:
Thanks to Anne for providing videos for this page.