[Usenet] To post a single article simultaneously to several newsgroups. 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.
Try this search on Wikipedia, OneLook, Google
Nearby terms: cross-assembler « cross-compiler « cross-platform « cross-post » cross software » CROSSTABS » crosstalk
