To delete a subdomain in cPanel, log in to your account and go to the Subdomains section under the Domains tab. There, you'll see a list of all the subdomains associated with your account.
Find the subdomain you want to remove and click the Remove button next to it.
Note: Deleting a subdomain will also delete all files and content stored in its associated directory—unless you’ve backed them up separately.
For more guidance, see our tutorial: How to Create Subdomains in cPanel.