This is a Search Property Filled 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 image shows a square filled with dots and lines signifying writing. There is a border at the top that gives the impression that this is an internet window. Overlapping the bottom corner of this window is a magnifying glass.