The Collaborative International Dictionary of English v.0.48:

homburg \hom"burg\ n. [from Homburg, Germany, the place of first
   manufacture.]
   A felt hat with a crown that is creased lengthwise, and a
   brim that is slightly curled upward at the edge.

   Syn: fedora, felt hat, trilby.
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

homburg
    n 1: a hat made of felt with a creased crown [syn: fedora,
         felt hat, homburg, Stetson, trilby]