The Collaborative International Dictionary of English v.0.48:

Ceylon \Ceylon\ n.
   the former name of an island republic in the Indian Ocean off
   the southeast coast of India, now called Sri Lanka. It is
   an independent nation with an area of 25,332 sq. mi. and a
   population of about 14 million people.

   Syn: Sri Lanka.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Ceylon
    n 1: an island in the Indian Ocean off the southeastern coast of
         India
    2: a republic on the island of Ceylon; became independent of the
       United Kingdom in 1948 [syn: Sri Lanka, Democratic
       Socialist Republic of Sri Lanka, Ceylon]