DuckCorp Dico

Found one definition

1.                 From The Collaborative International Dictionary of English v.0.48:
                   
   
   
                   
                     
   Cachet \Cach"et\, n. [F. fr. cacher to hide.]
      A seal, as of a letter.
      [1913 Webster]
      Lettre de cachet [F.], a sealed letter, especially a letter
         or missive emanating from the sovereign; -- much used in
         France before the Revolution as an arbitrary order of
         imprisonment.
         [1913 Webster] Cachexia