The Collaborative International Dictionary of English v.0.48:

Merchant \Mer"chant\, a.
   Of, pertaining to, or employed in, trade or merchandise; as,
   the merchant service.
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   Merchant bar, Merchant iron or Merchant steel, certain
      common sizes of wrought iron and steel bars.

   Merchant service or Merchant marine, the mercantile marine
      of a country. --Am. Cyc.

   Merchant ship, a ship employed in commerce.

   Merchant tailor, a tailor who keeps and sells materials for
      the garments which he makes.
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The Collaborative International Dictionary of English v.0.48:

Merchant \Mer"chant\, v. i.
   To be a merchant; to trade. [Obs.]
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The Collaborative International Dictionary of English v.0.48:

Merchant \Mer"chant\, n. [OE. marchant, OF. marcheant, F.
   marchand, fr. LL. mercatans, -antis, p. pr. of mercatare to
   negotiate, L. mercari to traffic, fr. merx, mercis, wares.
   See Market, Merit, and cf. Commerce.]
   1. One who traffics on a large scale, especially with foreign
      countries; a trafficker; a trader.
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            Others, like merchants, venture trade abroad.
                                                  --Shak.
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   2. A trading vessel; a merchantman. [Obs.] --Shak.
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   3. One who keeps a store or shop for the sale of goods; a
      shopkeeper. [U. S. & Scot.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

merchant
    n 1: a businessperson engaged in retail trade [syn: merchant,
         merchandiser]

The Devil's Dictionary (1881-1906):

MERCHANT, n.  One engaged in a commercial pursuit.  A commercial
pursuit is one in which the thing pursued is a dollar.