This is a Thunderbolt 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 12,900 icons, all in the same style and quality.
The icon is a logo of Thunderbolt. The icon has a bunker like shape, with what appears to be a long horizontal rectangular window in the center. There is also a lighting bolt with an arrow on the bottom of it, located directly on top of the bunker shaped object.