The Collaborative International Dictionary of English v.0.48:

Ilion \Ilion\ prop. n.
   Ilium, or Troy, the ancient city in Asia Minor that was the
   site of the Trojan War; -- a variant spelling of Ilium.

   Syn: Troy, Ilium.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Ilium \Il"i*um\, n. [See Ileum.] (Anat.)
   The dorsal one of the three principal bones comprising either
   lateral half of the pelvis; the dorsal or upper part of the
   hip bone. See Innominate bone, under Innominate. [Written
   also ilion, and ileum.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

Ilion
    n 1: an ancient city in Asia Minor that was the site of the
         Trojan War [syn: Troy, Ilion, Ilium]