Source : Webster's Revised Unabridged Dictionary (1913)

Rhythm \Rhythm\, n. [F. rhythme, rythme, L. rhythmus, fr. Gr.
   ??? measured motion, measure, proportion, fr. "rei^n to flow.
   See {Stream}.]
   1. In the widest sense, a dividing into short portions by a
      regular succession of motions, impulses, sounds, accents,
      etc., producing an agreeable effect, as in music poetry,
      the dance, or the like.

   2. (Mus.) Movement in musical time, with periodical
      recurrence of accent; the measured beat or pulse which
      marks the character and expression of the music; symmetry
      of movement and accent. --Moore (Encyc.)

   3. A division of lines into short portions by a regular
      succession of arses and theses, or percussions and
      remissions of voice on words or syllables.

   4. The harmonious flow of vocal sounds.

Source : WordNet®

rhythm
     n 1: the basic rhythmic unit in a piece of music; "the piece has
          a fast rhythm"; "the conductor set the beat" [syn: {beat},
           {musical rhythm}]
     2: recurring at regular intervals [syn: {regular recurrence}]
     3: an interval during which a recurring sequence of events
        occurs; "the neverending cycle of the seasons" [syn: {cycle},
         {round}]
     4: the arrangement of spoken words alternating stressed and
        unstressed elements; "the rhythm of Frost's poetry" [syn:
        {speech rhythm}]
     5: natural family planning in which ovulation is assumed to
        occur 14 days before the onset of a period (the fertile
        period would be assumed to extend from day 10 through day
        18 of her cycle) [syn: {rhythm method of birth control}, {rhythm
        method}, {calendar method of birth control}, {calendar
        method}]