Variations on lame delegations (terminology question)

[David Carmean]

My understanding of a "lame delegation" is that a listed nameserver for 
a zone is not authoritative for that zone.

What terminology is/should be used if the listed nameserver isn't 
a nameserver?  I.e. if it isn't and never does run a DNS nameserver?

And what if the NSDNAME of the NS record points to either a completely 
non-existant node, or that node has no address records (A or AAAA)?