The "swipe down" symbol here consists of a circle, with a straight line extending down from its lower half in the middle, with two diagonal, upward-reaching lines extending upwards from the end of the line. It is a circle with a downward-pointing arrow extending from it.
This icon is a part of a collection of Swipe Down flat icons produced by Icons8. Icons follow the guidelines of iOS, Windows, and Android and are designed by a single designer, guaranteeing the consistent quality.
Idea of Swipe Down Icon by Anonymous
We've received the idea on May 22, 2013 and created the icons on June 03, 2013
(Multi) touchscreen gestures iconse like these (but better ;) )