The Collaborative International Dictionary of English v.0.48:

Muffler \Muf"fler\, n.
   1. Anything used in muffling; esp., a scarf for protecting
      the head and neck in cold weather; a tippet.
      [1913 Webster]

            Fortune is painted blind, with a muffler above her
            eyes.                                 --Shak.
      [1913 Webster]

   2. (Mus.) A cushion for terminating or softening a note made
      by a stringed instrument with a keyboard.
      [1913 Webster]

   3. A kind of mitten or boxing glove, esp. when stuffed.
      [1913 Webster]

   4. One who muffles.
      [1913 Webster]

   5. (Mach.) Any of various devices to deaden the noise of
      escaping gases or vapors, as a tube filled with
      obstructions, through which the exhaust gases of an
      internal-combustion engine, as on an automobile, are
      passed (called also silencer).
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

muffler
    n 1: a tubular acoustic device inserted in the exhaust system
         that is designed to reduce noise [syn: silencer,
         muffler]
    2: a scarf worn around the neck
    3: a device that decreases the amplitude of electronic,
       mechanical, acoustical, or aerodynamic oscillations [syn:
       damper, muffler]