The Collaborative International Dictionary of English v.0.48:

Iran \I`ran"\ ([=e]`r[aum]n"), n. [Mod. Persian Ir[=a]n. Cf.
   Aryan.]
   The native name of Persia, the name adopted by the modern
   nation of Iran.
   [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

Iran
    n 1: a theocratic Islamic republic in the Middle East in western
         Asia; Iran was the core of the ancient empire that was
         known as Persia until 1935; rich in oil [syn: Iran,
         Islamic Republic of Iran, Persia]