Source : Free On-Line Dictionary of Computing

nslookup
     
        A {Unix} utility by Andrew Cherenson for querying {Internet}
        {domain name server}s.  The basic use is to find the {Internet
        address} corresponding to a given {hostname} (or vice versa).
        By changing the query type (e.g. "set type=CNAME") other types
        of information can be obtained including CNAME - the
        {canonical name} for an alias; HINFO - the host {CPU} and
        {operating system} type; MINFO - mailbox or mail list
        information; {MX} - {mail exchanger} information; NS - the
        {name server} for the named zone; PTR - the hostname if the
        query is an Internet address, otherwise the pointer to other
        information; SOA the domain's start-of-authority information;
        TXT - text information; UINFO - user information; WKS -
        supported {well-known service}s.  Other types (ANY, AXFR, MB,
        MD, MF, NULL) are described in {RFC 1035}.
     
       
     {(ftp://src.doc.ic.ac.uk/computing/operating-systems/unix/bsd-sources/usr.sbin/named/tools/nslookup/)}.
     
        (1994-10-27)