Is there a "standard" term that means "IP address or DNS name"?
No, AFAIK there's no standard term describing such.
If you really want to have this in a single DB table column, you should name it for what values could be there actually, e.g.
Though (depending on usage), you might prefer to have two distinct columns like
DNSName, since the IP-Address could be used directly with the client code accessing the database, while the DNS name needs some extra processing to determine the underlying IP-Address.
At least another boolean column like
IPAddrUsed might be helpful, to indicate what's really stored in that table column.