The Collaborative International Dictionary of English v.0.48:

Death's-head \Death's"-head`\, n.
   A naked human skull as the emblem of death; the head of the
   conventional personification of death.
   [1913 Webster]

         I had rather be married to a death's-head with a bone
         in his mouth.                            --Shak.
   [1913 Webster]

   Death's-head moth (Zool.), a very large European moth
      (Acherontia atropos), so called from a figure resembling
      a human skull on the back of the thorax; -- called also
      death's-head sphinx.
      [1913 Webster]