The Collaborative International Dictionary of English v.0.48:

grantor \grant"or\ (gr[.a]nt"[^o]r), n. (Law)
   The person by whom a grant or conveyance is made.
   [1913 Webster]

WordNet (r) 3.0 (2006):

grantor
    n 1: a person who makes a grant in legal form; "conveyed from
         grantor to grantee"

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "grantor":
   Maecenas, Santa Claus, almoner, almsgiver, angel, assignor,
   awarder, backer, bestower, cheerful giver, conferrer, consignor,
   contributor, donator, donor, fairy godmother, feoffor, financer,
   funder, giver, imparter, lady bountiful, patron, patroness,
   philanthropist, presenter, settler, subscriber, sugar daddy,
   supporter, testate, testator, testatrix, vouchsafer