The Collaborative International Dictionary of English v.0.48:

Grease \Grease\ (gr[=e]s), n. [OE. grese, grece, F. graisse;
   akin to gras fat, greasy, fr. LL. grassus thick, fat, gross,
   L. crassus. Cf. Crass.]
   1. Animal fat, as tallow or lard, especially when in a soft
      state; oily or unctuous matter of any kind.
      [1913 Webster]

   2. (Far.) An inflammation of a horse's heels, suspending the
      ordinary greasy secretion of the part, and producing
      dryness and scurfiness, followed by cracks, ulceration,
      and fungous excrescences.
      [1913 Webster]

   Grease bush. (Bot.) Same as Grease wood (below).

   Grease moth (Zool.), a pyralid moth (Aglossa pinguinalis)
      whose larva eats greasy cloth, etc.

   Grease wood (Bot.), a scraggy, stunted, and somewhat
      prickly shrub (Sarcobatus vermiculatus) of the Spinach
      family, very abundant in alkaline valleys from the upper
      Missouri to California. The name is also applied to other
      plants of the same family, as several species of
      Atriplex and Obione.
      [1913 Webster]