The Collaborative International Dictionary of English v.0.48:

Emporium \Em*po"ri*um\, n.; pl. Emporiums, L. Emporia. [L.,
   fr. Gr. ?, fr. ? belonging to commerce, fr. ? traveler,
   trader; ? in + ? way through and over, path. See In, and
   Empiric, Fare.]
   1. A place of trade; a market place; a mart; esp., a city or
      town with extensive commerce; the commercial center of a
      country.
      [1913 Webster]

            That wonderful emporium [Manchester] . . . was then
            a mean and ill-built market town.     --Macaulay.
      [1913 Webster]

            It is pride . . . which fills our streets, our
            emporiums, our theathers.             --Knox.
      [1913 Webster]

   2. (Physiol.) The brain. [Obs.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

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