DuckCorp Dico

Found one definition

1.                 From WordNet (r) 3.0 (2006):
                   
   
   
                   
                     
   sheath
       n 1: a protective covering (as for a knife or sword)
       2: an enveloping structure or covering enclosing an animal or
          plant organ or part [syn: sheath, case]
       3: a dress suitable for formal occasions [syn: cocktail dress,
          sheath]