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.
      [1913 Webster]

   2. To live by shifts and stratagems. --Beau. & Fl.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sharking \Shark"ing\, n.
   Petty rapine; trick; also, seeking a livelihood by shifts and
   dishonest devices.
   [1913 Webster]