The Collaborative International Dictionary of English v.0.48:

American \A*mer"i*can\ ([.a]*m[~e]r"[i^]*kan), a. [Named from
   Americus Vespucius.]
   1. Of or pertaining to America; as, the American continent:
      American Indians.
      [1913 Webster]

   2. Of or pertaining to the United States. "A young officer of
      the American navy." --Lyell.
      [1913 Webster]

   American ivy. See Virginia creeper.

   American Party (U. S. Politics), a party, about 1854, which
      opposed the influence of foreign-born citizens, and those
      supposed to owe allegiance to a foreign power.

   Native american Party (U. S. Politics), a party of
      principles similar to those of the American party. It
      arose about 1843, but soon died out.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

American \A*mer"i*can\ ([.a]*m[~e]r"[i^]*kan), n.
   A native of America; -- originally applied to the aboriginal
   inhabitants, but now applied to the descendants of Europeans
   born in America, and especially to the citizens of the United
   States.
   [1913 Webster]

         The name American must always exalt the pride of
         patriotism.                              --Washington.
   [1913 Webster]

WordNet (r) 3.0 (2006):

American
    adj 1: of or relating to the United States of America or its
           people or language or culture; "American citizens";
           "American English"; "the American dream"
    2: of or relating to or characteristic of the continents and
       islands of the Americas; "the American hemisphere"; "American
       flora and fauna"
    n 1: a native or inhabitant of the United States
    2: the English language as used in the United States [syn:
       American English, American language, American]
    3: a native or inhabitant of a North American or Central
       American or South American country