Source : Webster's Revised Unabridged Dictionary (1913)

Yataghan \Yat"a*ghan\, n. [Turk. y[=a]t[=a]gh[=a]n.]
   A long knife, or short saber, common among Mohammedan
   nations, usually having a double curve, sometimes nearly
   straight. [Written also {ataghan}, {attaghan}.] --Chaucer.

Source : WordNet®

yataghan
     n : a long Turkish knife with a curved blade having a single
         edge