Source : Webster's Revised Unabridged Dictionary (1913)

Rosin \Ros"in\, n. [A variant of resin.]
   The hard, amber-colored resin left after distilling off the
   volatile oil of turpentine; colophony.

   {Rosin oil}, an oil obtained from the resin of the pine tree,
      -- used by painters and for lubricating machinery, etc.