cross-post

or cross·post

[kraws-pohst kros‐]Digital Technology
verb (used with or without object)
  1. to post (the same message) to two or more message boards or electronic mailing lists at the same time.
noun
  1. a message posted to two or more message boards or electronic mailing lists at the same time: Cross-posts are often greeted with hostility.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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