The Collaborative International Dictionary of English v.0.48:

Shako \Shak"o\, n. [Hung. cs['a]k['o]: cf. F. shako, schako.]
   A kind of military cap or headdress.
   [1913 Webster]

WordNet (r) 3.0 (2006):

shako
    n 1: tall hat; worn by some British soldiers on ceremonial
         occasions [syn: bearskin, busby, shako]