Source : Webster's Revised Unabridged Dictionary (1913)

Busby \Bus"by\ (b[u^]z"b[y^]), n.; pl. {Busbies} (b[i^]z).
   (Mil.)
   A military headdress or cap, used in the British army. It is
   of fur, with a bag, of the same color as the facings of the
   regiment, hanging from the top over the right shoulder.