Definition of courtesy of
1 —used to say that something was paid for, given, or lent by a person, organization, business, etc. <This program is brought to you (by) courtesy of our sponsors.> <The flowers were provided through the courtesy of a local florist.> ; The word courtesy is sometimes used informally by itself in this way <Photo courtesy Helen Jones.>
2 informal used to indicate the cause of something <I have a bad cold now, courtesy of my brother.>
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