Source : Webster's Revised Unabridged Dictionary (1913)

Petrolatum \Pet`ro*la"tum\, n. (Chem. & Pharm.)
   A semisolid unctuous substance, neutral, and without taste or
   odor, derived from petroleum by distilling off the lighter
   portions and purifying the residue. It is a yellowish,
   fatlike mass, transparent in thin layers, and somewhat
   fluorescent. It is used as a bland protective dressing, and
   as a substitute for fatty materials in ointments. --U. S.
   Pharm.

   Note: Petrolatum is the official name for the purified
         product. Cosmoline and vaseline are commercial names
         for substances essentially the same, but differing
         slightly in appearance and consistency or fusibility.

Source : WordNet®

petrolatum
     n : a semi-solid mixture of hydrocarbons obtained from
         petroleum; used in medicinal ointments and for
         lubrication [syn: {petroleum jelly}, {mineral jelly}]