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.

Source: Webster's Revised Unabridged Dictionary (1913)
 

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

Or with the rosined bow torment the string. --Gay.

Source: Webster's Revised Unabridged Dictionary (1913)