Source : Webster's Revised Unabridged Dictionary (1913)

Guarantor \Guar"an*tor`\, n. [See {Guaranty}, and cf.
   {Warrantor}.] (Law)
   (a) One who makes or gives a guaranty; a warrantor; a surety.
   (b) One who engages to secure another in any right or
       possession.

Source : WordNet®

guarantor
     n : one who provides a warrant or guarantee to another [syn: {surety},
          {warrantor}, {warranter}]