Its a quarter circle input, so its the motion of moving the joystick from down, to the right (so it would essentially be down, down-right, right if you are doing it on a keyboard). This video might be handy: https://www.youtube.com/watch?v=9CDGGV_708Y

In most games it would be a little clearer with the arrow drawn around a joystick to signify the motion a bit better, but currently the move list just uses some engine-default icons that are a bit weird. I plan to change them in the future.