Default IP address in nameserver?

OK, I admit up front I'm still learning about DNS, but, if someone defines my nameservers as the nameservers for their domain, but I don't have any domain records for them in my nameservers, is there some way I can send someone who asks for their domain to a "default" IP address?

Does this make sense? This would amount to something like default domain parking.

Possible? I'm using djbdns.

-t

You mean that person doesn't know his IP or perhaps having a dynamic IP?
If you have plenty of static IP, you can just add an A record for his domain to park to one of your IP (12.34.56.78) temporarily to your data file (rebuild it to data.cdb) like so:

Zhisdomain.com:ns1.yourdns.com:hostmaster.yourdns.com
&hisdomain.com::ns1.yourdns.com
&hisdomain.com::ns2.yourdns.com
+hisdomain.com:12.34.56.78
+www.hisdomain.com:12.34.56.78

Anyway I am not quite sure what you are saying. If he defines the nameservers of yours for his domain without your permission, his domain would just reside nowhere on the internet.

That's exactly what I'm talking about. Someone who has defined my nameservers without my permission, and who's domain is now nowhere on the Internet. How can I "default park" that domain to one of my IP addresses, without knowing in advance it's pointed to my nameservers.

Sort of a default, or fall-through IP address for a domain that does not have any A records in my data file.

-t

>> without knowing in advance it's pointed to my nameservers

Unlike register.com that park your domain to one of their IPs only when you register with them. For your case, I see no sign you were informed in any ways that his domain should be parked at your servers. When you don't know anything about that domain, you just can't do it in advance.
Like I said in my previous post you can point his domain to one of your IPS temporarily. If you know someone is in process of transferring his domain to your nameserver, you do not have to wait, you can add his dns record to your data file immediately. The difference is that, your nameserver will not answer dns queries for his domain (others will not query your nameservers when you are not authoritative) when it's not yet transferred.