Source : Webster's Revised Unabridged Dictionary (1913)

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.

            Neither sharks for a cup or a reckoning. --Bp.
                                                  Earle.

   2. To live by shifts and stratagems. --Beau. & Fl.