The Collaborative International Dictionary of English v.0.48:

Shark \Shark\, v. i. [imp. & p. p. Sharked; p. pr. & vb. n.
   Sharking.]
   1. To play the petty thief; to practice fraud or trickery; to
      swindle.
      [1913 Webster]

            Neither sharks for a cup or a reckoning. --Bp.
                                                  Earle.
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   2. To live by shifts and stratagems. --Beau. & Fl.
      [1913 Webster]