Do Dictionaries Plagiarize?

Have you ever noticed that different dictionaries often define words almost exactly the same, word for word? Here are a few selected definitions of the word plagiarize from various dictionaries:

  1. to appropriate ideas, passages, etc., from (a work) by plagiarism
  2. to appropriate (ideas, passages, etc.) from (another work or author)
  3. to appropriate and pass off as one's own (the writings, ideas, etc., of another)
  4. to use and pass off (the ideas or writings of another) as one's own
  5. to steal and use (the ideas or writings of another) as one's own
  6. to steal and pass off as one's own (the ideas or words of another)

The sources are respectively:

  1. Webster's Encyclopedic Unabridged Dictionary of the English Language (based on the Random House Dictionary, 1st ed., 1994)
  2. The Collins Paperback English Dictionary (Collins, 1986)
  3. Standard Dictionary, International Edition (Vol. 2, Funk & Wagnalls, 1965)
  4. Dictionary.com (Lexico Publishing Group)
  5. The American Heritage Illustrated Encyclopedic Dictionary (Houghton Mifflin, 1982)
  6. Websters Third New International Dictionary (Merriam-Webster, 1993)

Is this plagiarism?

Update: At some time since this post, Dictionary.com started citing its sources, giving as a source for the entry "plagiarism", Random House Unabridged Dictionary, © Random House, Inc. 2006.