Open string whip is an offstring yo-yo trick that is done instead of a normal offstring throw.
To start this trick you want to throw the yo-yo like you would normally (during offstring play) would. Instead of grabbing the string let the yo-yo fly out from you a bit, then whip the string in a circle and bring it back to your hand.
The open end whip is a great crowd pleaser in the already awe-bringing style of 4a. Now to learn this trick, an offstring yo-yo(or a somewhat large yo-yo) is best to use. Such yo-yo's would be the YoYoJam aquarius, Big Ben, or Duncan Flying Panda. It is also better to have a thin gapped yo-yo, like the aquarius.
It is somewhat easy to learn this trick, but difficult to do consistantly. To do this trick, get the yo-yo spinning, pop the yo-yo up, and then whip the string in a circle and bring it into the gap. Once you start to get it, try to remember the motion you used to get it more consistently. This is a great trick to use after a regen, or right before a regen.