This is a Quick Mode On icon. We've made it in iOS style, first introduced in iOS version 7 and supported in all later releases up until now (at least iOS 11). This style is based on thin two-pixel lines and is optimized for 50x50 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 12,300 icons, all in the same style and quality.
It's the picture of a lightning bolt to indicate electricity. It is a single bolt of lightning, with no clouds or other features. It looks like the image of an hourglass, tilted about 45 degrees up, and then stretched out until it resembles a lightning bolt.