The Collaborative International Dictionary of English v.0.48:

duster \dust"er\ (d[u^]st"[~e]r), n.
   1. One who, or that which, dusts; a utensil that frees from
      dust. Specifically:
      (a) (Paper Making) A revolving wire-cloth cylinder which
          removes the dust from rags, etc.
      (b) (Milling) A blowing machine for separating the flour
          from the bran.
      (c) A dustcloth or a brush used for removing dust from
          objects or surfaces.
          [1913 Webster]

   2. A long light overgarment; specifically
      (a) a light over-garment, formerly worn when traveling in
          open vehicles to protect the clothing from dust.
          [U.S.]
      (b) A light housecoat worn by women.
      (c) A light overcoat worn by women, often having no
          lining.
          [1913 Webster +PJC]

   3. A device for spreading a powder, especially one for
      spreading insecticide on plants.
      [PJC]

   4. (Baseball) A pitch intentionally thrown by a pitcher
      directly at or very close to the batter, intended to make
      the batter stand further away from home plate; also called
      a dust-back pitch or a dust-back.
      [PJC]

   5. A dust storm.
      [PJC]

WordNet (r) 3.0 (2006):

duster
    n 1: a windstorm that lifts up clouds of dust or sand; "it was
         the kind of duster not experienced in years" [syn: dust
         storm, duster, sandstorm, sirocco]
    2: a loose coverall (coat or frock) reaching down to the ankles
       [syn: duster, gaberdine, gabardine, smock, dust
       coat]
    3: a piece of cloth used for dusting [syn: dustcloth,
       dustrag, duster]
    4: a pitch thrown deliberately close to the batter