The Collaborative International Dictionary of English v.0.48:

Sleep \Sleep\, n. [AS. sl[=ae]p; akin to OFries. sl[=e]p, OS.
   sl[=a]p, D. slaap, OHG. sl[=a]f, G. schlaf, Goth. sl[=e]ps.
   See Sleep, v. i.]
   A natural and healthy, but temporary and periodical,
   suspension of the functions of the organs of sense, as well
   as of those of the voluntary and rational soul; that state of
   the animal in which there is a lessened acuteness of sensory
   perception, a confusion of ideas, and a loss of mental
   control, followed by a more or less unconscious state. "A man
   that waketh of his sleep." --Chaucer.
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         O sleep, thou ape of death.              --Shak.
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   Note: Sleep is attended by a relaxation of the muscles, and
         the absence of voluntary activity for any rational
         objects or purpose. The pulse is slower, the
         respiratory movements fewer in number but more
         profound, and there is less blood in the cerebral
         vessels. It is susceptible of greater or less intensity
         or completeness in its control of the powers.
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   Sleep of plants (Bot.), a state of plants, usually at
      night, when their leaflets approach each other, and the
      flowers close and droop, or are covered by the folded
      leaves.
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   Syn: Slumber; repose; rest; nap; doze; drowse.
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