This Stopwatch 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 5,500 icons, all in the same style and quality.
A stopwatch is something that ticks and is handheld. It is circular with a little timer in the right so that you can click it and start + stop time. It has hands that keep track of how many seconds it has been.