From The Collaborative International Dictionary of English v.0.48 [gcide]:
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.
[1913 Webster]
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.)
[1913 Webster]
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.
[1913 Webster]
4. The harmonious flow of vocal sounds.
[1913 Webster]
From WordNet (r) 3.0 (2006) [wn]:
rhythm
n 1: the basic rhythmic unit in a piece of music; "the piece has
a fast rhythm"; "the conductor set the beat" [syn:
rhythm, beat, musical rhythm]
2: recurring at regular intervals [syn: rhythm, {regular
recurrence}]
3: an interval during which a recurring sequence of events
occurs; "the never-ending cycle of the seasons" [syn:
cycle, rhythm, round]
4: the arrangement of spoken words alternating stressed and
unstressed elements; "the rhythm of Frost's poetry" [syn:
rhythm, 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}, rhythm, calendar method of birth control,
calendar method]