The Collaborative International Dictionary of English v.0.48:

Aluminum \A*lu"mi*num\ ([.a]*l[=u]*m[i^]*n[u^]m), n.
   The metallic element forming the base of alumina. This metal
   is white, but with a bluish tinge, and is remarkable for its
   resistance to oxidation, and for its lightness, having a
   specific gravity of about 2.6. Atomic weight 27.08. Symbol
   Al. Also called aluminium.
   [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

Aluminium \Al`u*min"i*um\ ([a^]l`[-u]*m[i^]n"[i^]*[u^]m), n. [L.
   alumen. See Alum.] (Chem.)
   same as aluminum, chiefly British in usage.
   [1913 Webster]

   Aluminium bronze or gold, a pale gold-colored alloy of
      aluminium and copper, used for journal bearings, etc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

aluminium
    n 1: a silvery ductile metallic element found primarily in
         bauxite [syn: aluminum, aluminium, Al, atomic number
         13]

The Elements (07Nov00):

aluminium
Same as aluminum, chiefly British in usage. [1913 Webster]