The Collaborative International Dictionary of English v.0.48:

Whistle \Whis"tle\, v. t.
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   1. To form, utter, or modulate by whistling; as, to whistle a
      tune or an air.
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   2. To send, signal, or call by a whistle.
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            He chanced to miss his dog; we stood still till he
            had whistled him up.                  --Addison.
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   To whistle off.
      (a) To dismiss by a whistle; -- a term in hawking. "AS a
          long-winged hawk when he is first whistled off the
          fist, mounts aloft." --Burton.
      (b) Hence, in general, to turn loose; to abandon; to
          dismiss.
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                I 'ld whistle her off, and let her down the wind
                To prey at fortune.               --Shak.
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   Note: "A hawk seems to have been usually sent off in this
         way, against the wind when sent in search of prey; with
         or down the wind, when turned loose, and abandoned."
         --Nares.
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