Mapping Subdomain to a multisite

Is it possible to map a subdomain from another site to a subsite on multisite?

Example-
Subdomain: xyz.greatsite.com
Subsite on multisite: wow.bigsite.com

Yes, that should be possible.

Domain mapping works the same way, whether you’re mapping a full domain or sub-domain.

Now if someone visits xyz.greatsite.com he actually goes to wow.bigsite.com (While xyz.greatsite.com shows in the URL bar)

I’m lost 🙂

If you’re going through the trouble to map the external sub-domain wow.bigsite.com to the WordPress multisite sub-domain xyz.greatsite.com, why do you still want users to see xyz.greatsite.com?

Why don’t you want to make the multisite sub-domain xyz.greatsite.com work totally in the background and show the mapped domain wow.bigsite.com to users all the time?

Can you explain the rationale for this rather unorthodox setup?