Source : Webster's Revised Unabridged Dictionary (1913)

Squealer \Squeal"er\, n.
   1. One who, or that which, squeals.

   2. (Zo["o]l.)
      (a) The European swift.
      (b) The harlequin duck.
      (c) The American golden plover.

Source : WordNet®

squealer
     n 1: one who reveals confidential information in return for money
          [syn: {informer}, {betrayer}, {rat}, {blabber}]
     2: domestic swine [syn: {hog}, {pig}, {grunter}, {Sus scrofa}]