The Collaborative International Dictionary of English v.0.48:

Columbia \Co*lum"bi*a\, n.
   America; the United States; -- a poetical appellation given
   in honor of Columbus, the discoverer. --Dr. T. Dwight.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Columbia
    n 1: a North American river; rises in southwestern Canada and
         flows southward across Washington to form the border
         between Washington and Oregon before emptying into the
         Pacific; known for its salmon runs in the spring [syn:
         Columbia, Columbia River]
    2: a town in west central Tennessee
    3: capital and largest city in South Carolina; located in
       central South Carolina [syn: Columbia, capital of South
       Carolina]
    4: a university town in central Missouri
    5: a university in New York City [syn: Columbia University,
       Columbia]