A standard DNS subdomain record has a corresponding name such as blog.example.com. However, sometimes it may be necessary to enable Wildcard DNS which does not have a single record assigned. Instead of appearing as blog.example.com (or any other subdomain), it appears as *.example.com. The * character is used to match non-existing subdomain names.
Simply put, Wildcard DNS is used to provide DNS records for subdomains that do not exist.
How can I use a Wildcard DNS at DreamHost?
You can implement Wildcard DNS for domains that are running only on DreamHost’s Virtual Private Server plan. This is due to the extremely high resource usage (and potential abuse) that usually comes with installing software that relies on Wildcard DNS in order to function (i.e., WordPress Multi-User, or WPMU, and others).
DreamHost may, in special cases, set this up for a customer. This is a manual procedure for the support staff so please make sure that it's something that you absolutely need and that the domain in question is currently running on a VPS before requesting it. Please also make sure that you're aware of the technical implications of having a wildcard DNS entry set up on your domain.
If you need support
If you need Wildcard DNS set up for your domain, submit a support ticket on the (Panel > 'Support' > 'Contact Support') page.