Block/remove one WP-Multisite Subsite from search engines

Hi

I have one subsite of a wordpress multisite network, which must not be found on search engines. This subsite should be kind of private, but without a password.

I checked in the wordpress settings that this site should not be found on search engines – but I wonder if that is enough…

or is there a better way to make it more “private” without a password?

Thanks