The Collaborative International Dictionary of English v.0.48:

Grizzly \Griz"zly\, a.
   Somewhat gray; grizzled.
   [1913 Webster]

         Old squirrels that turn grizzly.         --Bacon.
   [1913 Webster]

   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.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Turkey-trot \Tur"key-trot`\, n.
   An eccentric ragtime dance, danced with the feet well apart
   and with a characteristic rise on the ball of the foot,
   followed by a drop upon the heel. The original form, owing to
   the positions assumed by the dancers, is offensively
   suggestive. Similar dances are the

   bunny hug and

   grizzly bear, so called in allusion to the movements and
      the positions assumed by the partners in dancing.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

grizzly bear
    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]