It's an exclamation point drawn inside of an equilateral triangle. The triangle is drawn with one side parallel to the ground, and the exclamation point is in the center of the triangle.
This Error icon is made in flat color style
. This format was developed by Icons8 designer team and became immensely popular for use in web and mobile applications. Feel free to download this icon in PNG format for free, or unlock other formats for $5. Unlike other icon packs that have merely hundreds of icons, this monster icon pack contains 6,000 icons, all in the same style and quality.