The Collaborative International Dictionary of English v.0.48:

Retailer \Re*tail"er\, n.
   One who retails anything; as, a retailer of merchandise; a
   retailer of gossip; -- used also of businesses, including
   large corporations; as, Sears, Roebuck is one the the
   country's largest retailers.
   [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

retailer
    n 1: a merchant who sells goods at retail [syn: retailer,
         retail merchant]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "retailer":
   caterer, chandler, commissariat, commissary, dealer, distributor,
   donor, furnisher, importer, jobber, manciple, marketer,
   merchandiser, merchant, middleman, monger, patron, provider,
   provisioner, purveyor, quartermaster, regrater, retail dealer,
   retail merchant, shopkeeper, steward, stock clerk, storekeeper,
   supplier, sutler, trader, tradesman, tradeswoman, trafficker,
   victualer, vivandier, wholesaler