The Collaborative International Dictionary of English v.0.48:

Gyration \Gy*ra"tion\ (j[-i]*r[=a]"sh[u^]n), n.
   1. The act of turning or whirling, as around a fixed center;
      a circular or spiral motion; motion about an axis;
      rotation; revolution.
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            The gyrations of an ascending balloon. --De Quincey.
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            If a burning coal be nimbly moved round in a circle,
            with gyrations continually repeated, the whole
            circle will appear like fire.         --Sir I.
                                                  Newton.
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   2. (Zool.) One of the whorls of a spiral univalve shell.
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   Center of gyration. (Mech.) See under Center.

   Radius of gyration, the distance between the axis of a
      rotating body and its center of gyration. --Rankine.
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