The Collaborative International Dictionary of English v.0.48:

Department store \De*part"ment store\
   A store keeping a great variety of goods which are arranged
   in several departments.
   [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

department store
    n 1: a large retail store organized into departments offering a
         variety of merchandise; commonly part of a retail chain
         [syn: department store, emporium]

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "department store":
   boutique, chain store, co-op, concession, cooperative,
   countinghouse, country store, dime store, discount house,
   discount store, emporium, establishment, five-and-ten,
   general store, house, magasin, mail-order house, market, mart,
   post, retail store, salon, shop, store, supermarket, trading post,
   variety shop, variety store, warehouse, wareroom,
   wholesale house