The Collaborative International Dictionary of English v.0.48:

Rosin \Ros"in\, n. [A variant of resin.]
   The hard, amber-colored resin left after distilling off the
   volatile oil of turpentine; colophony.
   [1913 Webster]

   Rosin oil, an oil obtained from the resin of the pine tree,
      -- used by painters and for lubricating machinery, etc.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Rosin \Ros"in\, v. t.
   To rub with rosin, as musicians rub the bow of a violin.
   [1913 Webster]

         Or with the rosined bow torment the string. --Gay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

rosin
    n 1: any of a class of solid or semisolid viscous substances
         obtained either as exudations from certain plants or
         prepared by polymerization of simple molecules [syn:
         resin, rosin]
    v 1: rub rosin onto; "rosin the violin bow"

Easton's 1897 Bible Dictionary:

Rosin
   found only in Authorized Version, margin, Ezek. 27:17, Heb.
   tsori, uniformly rendered elsewhere "balm" (q.v.), as here in
   the text. The Vulgate has resinam, rendered "rosin" in the Douay
   Version. As used, however, by Jerome, the Lat. resina denotes
   some odoriferous gum or oil.