Source : Free On-Line Dictionary of Computing

cross-post
     
        [{Usenet}] To post a single article simultaneously to several
        {newsgroup}s.  Distinguished from posting the article
        repeatedly, once to each newsgroup, which causes people to see
        it multiple times (which is very bad form).  Gratuitous
        cross-posting without a Followup-To line directing responses
        to a single followup group is frowned upon, as it tends to
        cause {followup} articles to go to inappropriate newsgroups
        when people respond to only one part of the original posting.
     
        [{Jargon File}]