The Collaborative International Dictionary of English v.0.48:

Carol \Car"ol\, v. t. [imp. & p. p. Caroled, or Carolled; p.
   pr. & vb. n. Caroling, or Carolling.]
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   1. To praise or celebrate in song.
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            The Shepherds at their festivals
            Carol her goodness.                   --Milton.
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   2. To sing, especially with joyful notes.
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            Hovering swans . . . carol sounds harmonious.
                                                  --Prior.
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