The Collaborative International Dictionary of English v.0.48:

Sing \Sing\ (s[i^]ng), v. t.
   1. To utter with musical inflections or modulations of voice.
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            And they sing the song of Moses, the servant of God,
            and the song of the Lamb.             --Rev. xv. 3.
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            And in the darkness sing your carol of high praise.
                                                  --Keble.
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   2. To celebrate in song; to give praises to in verse; to
      relate or rehearse in numbers, verse, or poetry. --Milton.
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            Arms and the man I sing.              --Dryden.
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            The last, the happiest British king,
            Whom thou shalt paint or I shall sing. --Addison.
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   3. To influence by singing; to lull by singing; as, to sing a
      child to sleep.
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   4. To accompany, or attend on, with singing.
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            I heard them singing home the bride.  --Longfellow.
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The Collaborative International Dictionary of English v.0.48:

Sing \Sing\ (s[i^]ng), v. i. [imp. Sungor Sang; p. p.
   Sung; p. pr. & vb. n. Singing.] [AS. singan; akin to D.
   zingen, OS. & OHG. singan, G. singen, Icel. syngja, Sw.
   sjunga, Dan. synge, Goth. siggwan, and perhaps to E. say,
   v.t., or cf. Gr. ??? voice. Cf. Singe, Song.]
   1. To utter sounds with musical inflections or melodious
      modulations of voice, as fancy may dictate, or according
      to the notes of a song or tune, or of a given part (as
      alto, tenor, etc.) in a chorus or concerted piece.
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            The noise of them that sing do I hear. --Ex. xxxii.
                                                  18.
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   2. To utter sweet melodious sounds, as birds do.
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            On every bough the briddes heard I sing. --Chaucer.
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            Singing birds, in silver cages hung.  --Dryden.
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   3. To make a small, shrill sound; as, the air sings in
      passing through a crevice.
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            O'er his head the flying spear
            Sang innocent, and spent its force in air. --Pope.
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   4. To tell or relate something in numbers or verse; to
      celebrate something in poetry. --Milton.
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            Bid her . . . sing
            Of human hope by cross event destroyed. --Prior.
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   5. To cry out; to complain. [Obs.]
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            They should sing if thet they were bent. --Chaucer.
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WordNet (r) 3.0 (2006):

sing
    v 1: deliver by singing; "Sing Christmas carols"
    2: produce tones with the voice; "She was singing while she was
       cooking"; "My brother sings very well"
    3: to make melodious sounds; "The nightingale was singing"
    4: make a whining, ringing, or whistling sound; "the kettle was
       singing"; "the bullet sang past his ear" [syn: whistle,
       sing]
    5: divulge confidential information or secrets; "Be careful--his
       secretary talks" [syn: spill the beans, let the cat out of
       the bag, talk, tattle, blab, peach, babble,
       sing, babble out, blab out] [ant: keep one's mouth
       shut, keep quiet, shut one's mouth]