The icon is an emoticon type face that is representing a sleeping person or sleepy emotion. The face has closed eyes and turned down mouth with an overall is calm expression.
This is a Sleeping 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 13,300 icons, all in the same style and quality.