The Collaborative International Dictionary of English v.0.48:

Blurt \Blurt\ (bl[^u]rt), v. t. [imp. & p. p. Blurted; p. pr.
   & vb. n. Blurting.] [Cf. Blare.]
   To utter suddenly and unadvisedly; to divulge
   inconsiderately; to ejaculate; -- commonly with out.
   [1913 Webster]

         Others . . . can not hold, but blurt out, those words
         which afterward they are forced to eat.  --Hakewill.
   [1913 Webster]

   To blurt at, to speak contemptuously of. [Obs.] --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

blurt
    v 1: utter impulsively; "He blurted out the secret"; "He
         blundered his stupid ideas" [syn: blurt out, blurt,
         blunder out, blunder, ejaculate]

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "blurt":
   allude to, babble, be indiscreet, be unguarded, betray,
   betray a confidence, blab, blabber, blurt out, burst out,
   call attention to, comment, disclose, divulge, ejaculate, exclaim,
   give away, inform, inform on, interject, leak, let drop, let fall,
   let slip, make reference to, mention, muse, note, observe, opine,
   peach, rat, refer to, reflect, remark, reveal, reveal a secret,
   sing, speak, spill, spill the beans, squeal, stool, talk, tattle,
   tattle on, tell on, tell secrets, tell tales, utter