The Collaborative International Dictionary of English v.0.48:

dusty \dust"y\ (d[u^]st"[y^]), a. [Compar. Dustier
   (d[u^]st"[i^]*[~e]r); superl. Dustiest
   (d[u^]st"[i^]*[e^]st).] [AS. dystig. See Dust.]
   1. Filled, covered, or sprinkled with dust; clouded with
      dust; as, a dusty table; a dusty attic; also, reducing to
      dust.
      [1913 Webster]

            And all our yesterdays have lighted fools
            The way to dusty death.               --Shak.
      [1913 Webster]

   2. Like dust; of the color of dust; as, a dusty white.
      [1913 Webster]

   Dusty miller (Bot.), a plant (Cineraria maritima); -- so
      called because of the ashy-white coating of its leaves.
      [1913 Webster]

WordNet (r) 3.0 (2006):

dusty miller
    n 1: shrubby perennial of the Canary Islands having white
         flowers and leaves and hairy stems covered with dustlike
         down; sometimes placed in genus Chrysanthemum [syn: dusty
         miller, silver-lace, silver lace, Tanacetum
         ptarmiciflorum, Chrysanthemum ptarmiciflorum]
    2: stiff much-branched perennial of the Mediterranean region
       having very white woolly stems and leaves [syn: dusty
       miller, Senecio cineraria, Cineraria maritima]
    3: a plant having leaves and stems covered with down that
       resembles dust [syn: dusty miller, Centaurea cineraria,
       Centaurea gymnocarpa]
    4: herb with greyish leaves found along the east coast of North
       America; used as an ornamental plant [syn: dusty miller,
       beach wormwood, old woman, Artemisia stelleriana]
    5: an old cottage garden plant of southeastern Europe widely
       cultivated for its attractive white woolly foliage and showy
       crimson flowers [syn: mullein pink, rose campion,
       gardener's delight, dusty miller, Lychnis coronaria]