The Collaborative International Dictionary of English v.0.48:

Guncotton \Gun"cot`ton\
   See under Gun.
   [1913 Webster]

WordNet (r) 3.0 (2006):

guncotton
    n 1: a nitric acid ester; used in lacquers and explosives [syn:
         cellulose nitrate, nitrocellulose, guncotton,
         nitrocotton]