Source : Webster's Revised Unabridged Dictionary (1913)

Mare \Mare\ (m[^a]r), n. [OE. mere, AS. mere, myre, fem of AS.
   mearh horse, akin to D. merrie mare, G. m["a]hre, OHG. marah
   horse, meriha mare, Icel. marr horse, OCelt. marka (Pausan.
   19, 19,4), Ir. marc, W. march. Cf. {Marshal}.]
   The female of the horse and other equine quadrupeds.

Mare \Mare\, n. [AS. mara incubus; akin to OHG. & Icel. mara;
   cf. Pol. mora, Bohem. m[*u]ra.] (Med.)
   Sighing, suffocative panting, intercepted utterance, with a
   sense of pressure across the chest, occurring during sleep;
   the incubus; -- obsolete, except in the compound nightmare.

         I will ride thee o' nights like the mare. --Shak.

Source : WordNet®

mare
     n 1: female equine animal [syn: {female horse}]
     2: a dark region of considerable extent on the surface of the
        moon [syn: {maria}]