The Collaborative International Dictionary of English v.0.48:

Mantelet \Man"tel*et\, n. [F., dim. of manteau, OF. mantel. See
   Mantle.]
   1.
      (a) A short cloak formerly worn by knights.
      (b) A short cloak or mantle worn by women.
          [1913 Webster]

                A mantelet upon his shoulders hanging.
                                                  --Chaucer.
          [1913 Webster]

   2. (Fort.) A musket-proof shield of rope, wood, or metal,
      which is sometimes used for the protection of sappers or
      riflemen while attacking a fortress, or of gunners at
      embrasures; -- now commonly written mantlet.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mantelet
    n 1: portable bulletproof shelter [syn: mantelet, mantlet]
    2: short cape worn by women [syn: mantelet, mantilla]