Three z letters chained together indicating that someone is sleeping or wanting to sleep. The zzz emoji can also be used to indicate tiredness or that someone is boring.
The zzz emoji was introduced in 2010 and released as part of the Unicode 11.0 standard. This emoji can be found under the smileys and emotions
category. Because the zzz emoji has been around for quite some time, it should display correctly in the majority of operating systems.