The Collaborative International Dictionary of English v.0.48:

Gentile \Gen"tile\, a.
   1. Belonging to the nations at large, as distinguished from
      the Jews; ethnic; of pagan or heathen people.
      [1913 Webster]

   2. (Gram.) Denoting a race or country; as, a gentile noun or
      adjective.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Gentile \Gen"tile\ (j[e^]n"t[imac]l), n. [L. gentilis belonging
   to the same clan, stock, race, people, or nation; in
   opposition to Roman, a foreigner; in opposition to Jew or
   Christian, a heathen: cf. F. gentil. See Gentle, a.]
   1. One neither a Jew nor a Christian; a worshiper of false
      gods; a heathen.
      [1913 Webster]

   2. A person who is not Jewish; -- used in this sense by Jews.

   Syn: goy[male], shiksa[female].
        [PJC]

   Note: The Hebrews included in the term g[=o]yim, or nations,
         all the tribes of men who had not received the true
         faith, and were not circumcised. The Christians
         translated g[=o]yim by the L. gentes, and imitated the
         Jews in giving the name gentiles to all nations who
         were neither Jews nor Christians. In civil affairs, the
         denomination was given to all nations who were not
         Romans. As used by Mormons, the term gentile designates
         any person who is not a Mormon.

   Syn: Pagan; heathen. See Pagan.
        [1913 Webster]

WordNet (r) 3.0 (2006):

gentile
    adj 1: belonging to or characteristic of non-Jewish peoples
    n 1: a person who does not acknowledge your god [syn: heathen,
         pagan, gentile, infidel]
    2: a person who is not a member of one's own religion; used in
       this sense by Mormons and Hindus
    3: a Christian as contrasted with a Jew [syn: gentile, non-
       Jew, goy]
    4: a Christian; "Christians refer to themselves as gentiles"

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "gentile":
   atheist, atheistic, clannish, disbeliever, ethnic, family, genetic,
   gentilic, giaour, goy, goyish, heathen, infidel, infidelic, kaffir,
   lineal, minimifidian, misbelieving, national, non-Christian,
   non-Jew, non-Jewish, non-Mohammedan, non-Mormon, non-Moslem,
   non-Muhammadan, non-Muslim, nonbeliever, nullifidian, pagan,
   phyletic, phylogenetic, profane, racial, secularist, shegets,
   shiksa, totemic, tribal, unbeliever, unbelieving, unchristian,
   uncircumcised, zendician, zendik, zendikite