Part of macOS
com.apple.WebKit.WebContent…Web page
◐ Close the app instead
One web page in Safari, Mail or another app that shows web content.
What it is
Each open web page runs in one of these, so a broken page can’t crash the rest.
Why it might be busy
A page is playing video, running a web app or stuck. Usually until you close that page.
If you stop it
That page goes blank and asks to reload. Close the tab or app instead.
The verdict
◐ Close the app instead. A part of an app. Closing it alone breaks something, so close its app.
In Activity Monitor
com.apple.WebKit.WebContent…
… means any name that starts this way.
From Procession’s guide, in the words the app shows.