Carol, 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.
3 other Webster entries under this spelling
Carol, n.
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.
Carol, 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 awans . . . carol sounds harmonious. Prior.
Carol, Carrol, n.
(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.
Shades of meaning
Fernald has no entry of its own for carol; he lists it under sing.
Where he writes about it:
To carol is to sing joyously, and to warble (kindred with whirl) is to sing with trills or quavers, usually also with the idea of joy. — from sing
Carol and warble are especially applied to the singing of birds. — from sing