This is a rectangular box with a indent pointing left on the left hand side. On the outside top and bottom of the box are 3 lines that radiate out at different angles. Inside of the box are three lines representing text.
This Hint 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.