The Collaborative International Dictionary of English v.0.48:

amalgam \a*mal"gam\ ([.a]*m[a^]l"gam), n. [F. amalgame, prob.
   fr. L. malagma, Gr. ma`lagma, emollient, plaster, poultice,
   fr. mala`ssein to make soft, fr. malako`s soft.]
   1. An alloy of mercury with another metal or metals; as, an
      amalgam of tin, bismuth, etc.
      [1913 Webster]

   Note: Medalists apply the term to soft alloys generally.
         [1913 Webster]

   2. A mixture or compound of different things.
      [1913 Webster]

   3. (Min.) A native compound of mercury and silver.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

amalgam \a*mal"gam\, v. t. & i. [Cf. F. amalgamer]
   To amalgamate. --Boyle. --B. Jonson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

amalgam
    n 1: an alloy of mercury with another metal (usually silver)
         used by dentists to fill cavities in teeth; except for iron
         and platinum all metals dissolve in mercury and chemists
         refer to the resulting mercury mixtures as amalgams [syn:
         amalgam, dental amalgam]
    2: a combination or blend of diverse things; "his theory is an
       amalgam of earlier ideas"

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "amalgam":
   admixture, alloy, alloyage, amalgamation, blend, combination,
   combo, commixture, composite, composition, compound, concoction,
   confection, ensemble, fusion, immixture, interfusion, intermixture,
   magma, mix, mixture, paste