Yes, as long as you have Windows Updates set to automatically install.
But if you don’t, what then? Unless I have missed something I can find no built-in option to allow for Windows Defender definition updates and scheduling.
I personally prefer to review updates and install them when I choose. I find it unfortunate Microsoft doesn’t allow for a higher level of user customization in regards to Windows updates.
So… what I have done in order to keep my Windows Defender up-to-date is create a task in Task Scheduler. After you open Task Scheduler in Administrative Tools, or by searching for “Schedule Tasks”, you will see there is already a Windows Defender section. Here is where you can add the update task. Below are screen shots of my configuration you can use as a starting point.
If you are curious what else MpCmdRun.exe can do just type the following at a command prompt:
“C:\Program Files\Windows Defender\MpCmdRun.exe” /?