Source : Webster's Revised Unabridged Dictionary (1913)

Spritsail \Sprit"sail\ (? or ?), n. (Naut.)
   (a) A sail extended by a sprit.
   (b) A sail formerly hung under the bowsprit, from the
       spritsail yard.

Source : WordNet®

spritsail
     n : a fore-and-aft sail extended by a sprit