Source : Webster's Revised Unabridged Dictionary (1913)

Squeal \Squeal\, v. i. [imp. & p. p. {Squealed}; p. pr. & vb. n.
   {Squealing}.] [Of Scand. origin; cf. Sw. sqv["a]la, Norw.
   skvella. Cf. {Squeak}, {Squall}.]
   1. To cry with a sharp, shrill, prolonged sound, as certain
      animals do, indicating want, displeasure, or pain.

   2. To turn informer; to betray a secret. [Slang]