The Collaborative International Dictionary of English v.0.48:

Barker \Bark"er\, n.
   1. An animal that barks; hence, any one who clamors
      unreasonably.
      [1913 Webster]

   2. One who stands at the doors of shops to urg? passers by to
      make purchases. [Cant, Eng.]
      [1913 Webster]

   3. A pistol. [Slang] --Dickens.
      [1913 Webster]

   4. (Zool.) The spotted redshank.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Barker \Bark"er\, n.
   One who strips trees of their bark.
   [1913 Webster]

WordNet (r) 3.0 (2006):

barker
    n 1: someone who stands in front of a show (as at a carnival)
         and gives a loud colorful sales talk to potential customers
    2: informal terms for dogs [syn: pooch, doggie, doggy,
       barker, bow-wow]