NOUN (2)

1. one of the islands of Saint Christopher-Nevis;

2. a straw hat with a tall crown and broad brim; worn in American southwest and in Mexico;

The Collaborative International Dictionary of English v.0.48:

Sombrero \Som*bre"ro\, n. [Sp., from sombra shade. See
   Sombre.]
   A kind of broad-brimmed hat, worn in Spain and in Spanish
   America. --Marryat.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Sombrero
    n 1: one of the islands of Saint Christopher-Nevis
    2: a straw hat with a tall crown and broad brim; worn in
       American southwest and in Mexico