The Collaborative International Dictionary of English v.0.48:

Glengarry \Glen*gar"ry\, n., or Glengarry bonnet \Glen*gar"ry
bon"net\ [Name of a valley in Scotland.]
   A kind of Highland Scotch cap for men, with straight sides
   and a hollow top sloping to the back, where it is parted and
   held together by ribbons or strings.

         The long silk streamers of his Glengarry bonnet. --L.
                                                  Hutton.
   [Webster 1913 Suppl.] Glenlivat

WordNet (r) 3.0 (2006):

Glengarry
    n 1: a Scottish cap with straight sides and a crease along the
         top from front to back; worn by Highlanders as part of
         military dress