The Collaborative International Dictionary of English v.0.48:

Rustle \Rus"tle\, v. i. [imp. & p. p. Rustled; p. pr. & vb. n.
   Rustling.] [AS. hristlan to rustle; or cf. Sw. rusta to
   stir, make a riot, or E. rush, v.]
   1. To make a quick succession of small sounds, like the
      rubbing or moving of silk cloth or dry leaves.
      [1913 Webster]

            He is coming; I hear his straw rustle. --Shak.
      [1913 Webster]

            Prouder than rustling in unpaid-for silk. --Shak.
      [1913 Webster]

   2. To stir about energetically; to strive to succeed; to
      bustle about. [Slang, Western U.S.]
      [1913 Webster]

   3. To steal; -- used of livestock and esp. of cattle.
      [PJC]

   To rustle up To gather or find by searching; as, to rustle
      up some food for supper.
      [PJC]

WordNet (r) 3.0 (2006):

rustling
    adj 1: characterized by soft sounds; "a murmurous brook"; "a
           soughing wind in the pines"; "a slow sad susurrous rustle
           like the wind fingering the pines"- R.P.Warren [syn:
           murmurous, rustling, soughing, susurrous]
    n 1: the stealing of cattle
    2: a light noise, like the noise of silk clothing or leaves
       blowing in the wind [syn: rustle, rustling, whisper,
       whispering]