The Collaborative International Dictionary of English v.0.48:

Cycle \Cy"cle\ (s?"k'l), n. [F. ycle, LL. cyclus, fr. Gr.
   ky`klos ring or circle, cycle; akin to Skr. cakra wheel,
   circle. See Wheel.]
   1. An imaginary circle or orbit in the heavens; one of the
      celestial spheres. --Milton.
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   2. An interval of time in which a certain succession of
      events or phenomena is completed, and then returns again
      and again, uniformly and continually in the same order; a
      periodical space of time marked by the recurrence of
      something peculiar; as, the cycle of the seasons, or of
      the year.
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            Wages . . . bear a full proportion . . . to the
            medium of provision during the last bad cycle of
            twenty years.                         --Burke.
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   3. An age; a long period of time.
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            Better fifty years of Europe than a cycle of Cathay.
                                                  --Tennyson.
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   4. An orderly list for a given time; a calendar. [Obs.]
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            We . . . present our gardeners with a complete cycle
            of what is requisite to be done throughout every
            month of the year.                    --Evelyn.
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   5. The circle of subjects connected with the exploits of the
      hero or heroes of some particular period which have served
      as a popular theme for poetry, as the legend of Arthur and
      the knights of the Round Table, and that of Charlemagne
      and his paladins.
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   6. (Bot.) One entire round in a circle or a spire; as, a
      cycle or set of leaves. --Gray.
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   7. A bicycle or tricycle, or other light velocipede.
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   8. A motorcycle.
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   9. (Thermodynamics) A series of operations in which heat is
      imparted to (or taken away from) a working substance which
      by its expansion gives up a part of its internal energy in
      the form of mechanical work (or being compressed increases
      its internal energy) and is again brought back to its
      original state.
      [Webster 1913 Suppl.]

   10. (Technology) A complete positive and negative, or forward
       and reverse, action of any periodic process, such as a
       vibration, an electric field oscillation, or a current
       alternation; one period. Hence: (Elec.) A complete
       positive and negative wave of an alternating current. The
       number of cycles (per second) is a measure of the
       frequency of an alternating current.
       [Webster 1913 Suppl. + PJC]

   Calippic cycle, a period of 76 years, or four Metonic
      cycles; -- so called from Calippus, who proposed it as an
      improvement on the Metonic cycle.

   Cycle of eclipses, a period of about 6,586 days, the time
      of revolution of the moon's node; -- called Saros by the
      Chaldeans.

   Cycle of indiction, a period of 15 years, employed in Roman
      and ecclesiastical chronology, not founded on any
      astronomical period, but having reference to certain
      judicial acts which took place at stated epochs under the
      Greek emperors.

   Cycle of the moon, or Metonic cycle, a period of 19
      years, after the lapse of which the new and full moon
      returns to the same day of the year; -- so called from
      Meton, who first proposed it.

   Cycle of the sun, Solar cycle, a period of 28 years, at
      the end of which time the days of the month return to the
      same days of the week. The dominical or Sunday letter
      follows the same order; hence the solar cycle is also
      called the cycle of the Sunday letter. In the Gregorian
      calendar the solar cycle is in general interrupted at the
      end of the century.
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