The Collaborative International Dictionary of English v.0.48:

Whipsaw \Whip"saw`\, n.
   1. A saw for dividing timber lengthwise, usually set in a
      frame, and worked by two persons; also, a fret saw.
      [1913 Webster]

   2. A kind of narrow ripsaw, tapering from butt to point, with
      hook teeth and averaging from 5 to 71/2 feet in length,
      used by one or two men.
      [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Whipsaw \Whip"saw`\, v. t.
   1. To saw with the whipsaw.
      [Webster 1913 Suppl.]

   2. To defeat in, or cause to lose, two different bets at the
      same turn or in one play, as a player at faro who has made
      two bets at the same time, one that a card will lose and
      another that a different card will win; hence, to defeat
      in spite of every effort.
      [Webster 1913 Suppl.]

   3. to cause to suffer a setback or losses by subjecting to
      two forces at the same time or in rapid succession; as,
      consumers were whipsawed by both inflation and higher
      sales taxes.
      [PJC]

   4. (Finance) to cause to suffer a series of losses in trading
      when buying and selling at the wrong times in a rapidly
      fluctuating market; -- especially used when an attempt is
      made, by selling short, to recover losses from a long
      purchase in a declining market, and the short sale also
      results in a loss when the market subsequently rises. Used
      mostly in the passive; as, to be whipsawed by exaggerated
      responses to a changing outlook.
      [PJC]

WordNet (r) 3.0 (2006):

whipsaw
    n 1: a saw with handles at both ends; intended for use by two
         people [syn: two-handed saw, whipsaw, two-man saw,
         lumberman's saw]
    v 1: victimize, especially in gambling or negotiations
    2: saw with a whipsaw