The Collaborative International Dictionary of English v.0.48:

Buyer \Buy"er\ (b[imac]"[~e]r), n.
   One who buys; a purchaser.
   [1913 Webster]

WordNet (r) 3.0 (2006):

buyer
    n 1: a person who buys [syn: buyer, purchaser, emptor,
         vendee]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

BUYER, contracts. A purchaser; (q. v.) a vendee.