The Collaborative International Dictionary of English v.0.48:

Grizzly \Griz"zly\, a.
   Somewhat gray; grizzled.
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         Old squirrels that turn grizzly.         --Bacon.
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   Grizzly bear (Zool.), a large and ferocious bear (Ursus
      horribilis) of Western North America and the Rocky
      Mountains. It is remarkable for the great length of its
      claws.
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The Collaborative International Dictionary of English v.0.48:

Bear \Bear\ (b[^a]r), n. [OE. bere, AS. bera; akin to D. beer,
   OHG. bero, pero, G. b[aum]r, Icel. & Sw. bj["o]rn, and
   possibly to L. fera wild beast, Gr. fh`r beast, Skr. bhalla
   bear.]
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   1. (Zool.) Any species of the genus Ursus, and of the
      closely allied genera. Bears are plantigrade Carnivora,
      but they live largely on fruit and insects.
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   Note: The European brown bear (Ursus arctos), the white
         polar bear (Ursus maritimus), the grizzly bear
         (Ursus horribilis), the American black bear, and its
         variety the cinnamon bear (Ursus Americanus), the
         Syrian bear (Ursus Syriacus), and the sloth bear, are
         among the notable species.
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   2. (Zool.) An animal which has some resemblance to a bear in
      form or habits, but no real affinity; as, the woolly bear;
      ant bear; water bear; sea bear.
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   3. (Astron.) One of two constellations in the northern
      hemisphere, called respectively the Great Bear and the
      Lesser Bear, or Ursa Major and Ursa Minor.
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   4. Metaphorically: A brutal, coarse, or morose person.
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   5. (Stock Exchange) A person who sells stocks or securities
      for future delivery in expectation of a fall in the
      market.
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   Note: The bears and bulls of the Stock Exchange, whose
         interest it is, the one to depress, and the other to
         raise, stocks, are said to be so called in allusion to
         the bear's habit of pulling down, and the bull's of
         tossing up.
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   6. (Mach.) A portable punching machine.
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   7. (Naut.) A block covered with coarse matting; -- used to
      scour the deck.
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   Australian bear. (Zool.) See Koala.

   Bear baiting, the sport of baiting bears with dogs.

   Bear caterpillar (Zool.), the hairy larva of a moth, esp.
      of the genus Euprepia.

   Bear garden.
      (a) A place where bears are kept for diversion or
          fighting.
      (b) Any place where riotous conduct is common or
          permitted. --M. Arnold.

   Bear leader, one who leads about a performing bear for
      money; hence, a facetious term for one who takes charge of
      a young man on his travels.
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WordNet (r) 3.0 (2006):

Ursus horribilis
    n 1: powerful brownish-yellow bear of the uplands of western
         North America [syn: grizzly, grizzly bear, silvertip,
         silver-tip, Ursus horribilis, Ursus arctos
         horribilis]