I/O wait (iowait) is the percentage of time that the CPU (or CPUs) were idle during which the system had pending disk I/O requests.

What does Iowait mean?

IOWait (usually labeled %wa in top) is a sub-category of idle (%idle is usually expressed as all idle except defined subcategories), meaning the CPU is not doing anything.

What is I O wait in Linux?

iowait is simply a form of idle time when nothing could be scheduled. The value may or may not be useful in indicating a performance problem, but it does tell the user that the system is idle and could have taken more work.