'Staysail' definitions:

Definition of 'staysail'

(from WordNet)
noun
A fore-and-aft sail set on a stay (as between two masts)

Definition of 'Staysail'

From: GCIDE
  • Staysail \Stay"sail`\ (st[=a]"s[=a]l`;among sailors, st[=a]"s'l), n. (Naut.) Any sail extended on a stay. [1913 Webster]