Source : Webster's Revised Unabridged Dictionary (1913)

Carol \Car"ol\, v. t. [imp. & p. p. {Caroled}, or {Carolled}; p.
   pr. & vb. n. {Caroling}, or {Carolling}.]
   1. To praise or celebrate in song.

            The Shepherds at their festivals Carol her goodness.
                                                  --Milton.

   2. To sing, especially with joyful notes.

            Hovering swans . . . carol sounds harmonious.
                                                  --Prior.

Carol \Car"ol\, v. i.
   To sing; esp. to sing joyfully; to warble.

         And carol of love's high praise.         --Spenser.

         The gray linnets carol from the hill.    --Beattie.

Carol \Car"ol\, Carrol \Car"rol\, n. [OF. carole a sort of
   circular space, or carol.] (Arch.)
   A small closet or inclosure built against a window on the
   inner side, to sit in for study. The word was used as late as
   the 16th century.

         A bay window may thus be called a carol. --Parker.

Carol \Car"ol\, n. [OF. carole a kind of dance wherein many
   dance together, fr. caroler to dance; perh. from Celtic; cf.
   Armor. koroll, n., korolla, korolli, v., Ir. car music, turn,
   circular motion, also L. choraula a flute player, charus a
   dance, chorus, choir.]
   1. A round dance. [Obs.] --Chaucer.

   2. A song of joy, exultation, or mirth; a lay.

            The costly feast, the carol, and the dance. --Dryden

            It was the carol of a bird.           --Byron.

   3. A song of praise of devotion; as, a Christmas or Easter
      carol.

            Heard a carol, mournful, holy.        --Tennyson.

            In the darkness sing your carol of high praise.
                                                  --Keble.

   4. Joyful music, as of a song.

            I heard the bells on Christmans Day Their old,
            familiar carol play.                  --Longfellow.

Source : WordNet®

carol
     n 1: joyful religious song celebrating the birth of Christ [syn:
          {Christmas carol}]
     2: a joyful song (usually celebrating the birth of Christ)
     [also: {carolling}, {carolled}]

carol
     v : sing carols; "They went caroling on Christmas Day"
     [also: {carolling}, {carolled}]