Source : Webster's Revised Unabridged Dictionary (1913)

Spread \Spread\, n.
   1. An arbitrage transaction operated by buying and selling
      simultaneously in two separate markets, as Chicago and New
      York, when there is an abnormal difference in price
      between the two markets. It is called a

   {back spread}when the difference in price is less than the
      normal one.

   2. (Gems) Surface in proportion to the depth of a cut stone.