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]

Moby Thesaurus II by Grady Ward, 1.0:

215 Moby Thesaurus words for "sing":
   anthem, babble, ballad, bark, bawl, be in heaven, be indiscreet,
   be pleased, be unguarded, beam, bellow, betray,
   betray a confidence, blab, blabber, blare, blat, blow the whistle,
   blubber, blurt, blurt out, boom, bray, breathe, buzz, cackle, call,
   caper, caracole, carol, caw, chant, chatter, cheep, chirk, chirp,
   chirr, chirrup, chitter, choir, choral service, chorus, chuck,
   clack, clap hands, climb Parnassus, cluck, cock-a-doodle-doo,
   compose poetry, coo, croak, cronk, croon, crow, cuckoo, dance,
   delight, descant, die with delight, do-re-mi, drawl, drum,
   eisteddfod, elegize, exclaim, exult, farewell performance,
   feel happy, flute, folk-music festival, folk-sing, frisk, frolic,
   gabble, gaggle, gambol, gasp, give away, glory, glow,
   go into raptures, gobble, groan, growl, grunt, guggle, hiss, honk,
   hoo, hoot, hootenanny, howl, hum, hymn, inform, inform on,
   intonate, intone, jam session, joy, jubilate, keen, laugh, leak,
   let drop, let fall, let slip, lilt, lisp in numbers, lull, lullaby,
   make immortal verse, minstrel, moan, mount Pegasus, mumble, murmur,
   music festival, musicale, mutter, nark, opera festival, pant,
   peach, peep, pimp, pip, pipe, poetize, psalm, purr, quack, quaver,
   radiate cheer, rat, rejoice, reveal a secret, revel, roar,
   rock festival, roll, rollick, romp, roulade, rumble, scold, scream,
   screech, serenade, service of song, shake, shriek, sibilate, sigh,
   sing deathless songs, sing in chorus, sing-in, singfest, singing,
   singsong, skip, skip for joy, smile, snap, snarl, snitch, snort,
   sob, sol-fa, solmizate, sough, sparkle, spill, spill the beans,
   squall, squawk, squeak, squeal, stool, swan song,
   take great satisfaction, talk, tattle, tattle on, tell, tell on,
   tell secrets, tell tales, thunder, tread on air, tremolo, trill,
   troll, trumpet, tune, twang, tweedle, tweedledee, tweet, twit,
   twitter, verse, versify, vocalize, wail, warble, whine, whisper,
   whistle, write poetry, yap, yawp, yell, yelp, yodel