Source : Webster's Revised Unabridged Dictionary (1913)

Mule \Mule\ (m[=u]l), n. [F., a she-mule, L. mula, fem. of
   mulus; cf. Gr. my`klos, mychlo`s. Cf. AS. m[=u]l, fr. L.
   mulus. Cf. {Mulatto}.]
   1. (Zo["o]l.) A hybrid animal; specifically, one generated
      between an ass and a mare, sometimes a horse and a
      she-ass. See {Hinny}.

   Note: Mules are much used as draught animals. They are hardy,
         and proverbial for stubbornness.

   2. (Bot.) A plant or vegetable produced by impregnating the
      pistil of one species with the pollen or fecundating dust
      of another; -- called also {hybrid}.

   3. A very stubborn person.

   4. A machine, used in factories, for spinning cotton, wool,
      etc., into yarn or thread and winding it into cops; --
      called also {jenny} and {mule-jenny}.

   {Mule armadillo} (Zo["o]l.), a long-eared armadillo (Tatusia
      hybrida), native of Buenos Aires; -- called also {mulita}.
      See Illust. under {Armadillo}.

   {Mule deer} (Zo["o]l.), a large deer ({Cervus, or Cariacus,
      macrotis}) of the Western United States. The name refers
      to its long ears.

   {Mule pulley} (Mach.), an idle pulley for guiding a belt
      which transmits motion between shafts that are not
      parallel.

   {Mule twist}, cotton yarn in cops, as spun on a mule; -- in
      distinction from yarn spun on a throstle frame.

Source : WordNet®

mule
     n 1: sterile offspring of a male donkey and a female horse
     2: a slipper that has no fitting around the heel [syn: {mules},
         {scuff}, {scuffs}]

Source : Free On-Line Dictionary of Computing

Mule
     
         A multi-lingual enhancement of {GNU Emacs}.  Mule
        can handle not only {ASCII} characters (7 bit) and {ISO
        Latin 1} characters (8 bit), but also {16-bit characters} like
        Japanese, Chinese, and Korean.  Mule can have a mixture of
        languages in a single buffer.
     
        Mule runs under the {X window system}, or on a {Hangul
        terminal}, {mterm} or {exterm}.
     
        Latest version: 2.3.
     
        {Home (ftp://etlport.etl.go.jp/pub/mule)}.
     
        (1996-01-28)