Source : Webster's Revised Unabridged Dictionary (1913)

Lubricant \Lu"bri*cant\, a. [L. lubricans, p. pr. of lubricare,
   See {Lubricate}.]
   Lubricating.

Lubricant \Lu"bri*cant\, n.
   That which lubricates; specifically, a substance, as oil,
   grease, plumbago, etc., used for reducing the friction of the
   working parts of machinery.

Source : WordNet®

lubricant
     n : a substance capable of reducing friction by making surfaces
         smooth or slippery [syn: {lubricator}, {lubricating
         substance}]