The icon is a picture for the logo Octahedron. The icon is a picture of what looks to be an 8 sided die. The die is in the shape of an 8 sided diamond. The die has the number eight visible on the front of it.
This Octahedron icon is made in Material Design style
developed by Google. This style is based on extremely simplified shapes, thin two-pixel lines, and is optimized for 24x24 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 5,700 icons, all in the same style and quality.