The Collaborative International Dictionary of English v.0.48:

Prostration \Pros*tra"tion\, n. [L. prostratio: cf. F.
   prostration.]
   1. The act of prostrating, throwing down, or laying fiat; as,
      the prostration of the body.
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   2. The act of falling down, or of bowing in humility or
      adoration; primarily, the act of falling on the face, but
      usually applied to kneeling or bowing in reverence and
      worship.
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            A greater prostration of reason than of body.
                                                  --Shak.
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   3. The condition of being prostrate; great depression;
      lowness; dejection; as, a postration of spirits. "A sudden
      prostration of strength." --Arbuthnot.
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   4. (Med.) A latent, not an exhausted, state of the vital
      energies; great oppression of natural strength and vigor.
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   Note: Prostration, in its medical use, is analogous to the
         state of a spring lying under such a weight that it is
         incapable of action; while exhaustion is analogous to
         the state of a spring deprived of its elastic powers.
         The word, however, is often used to denote any great
         depression of the vital powers.
         [1913 Webster]

WordNet (r) 3.0 (2006):

prostration
    n 1: an abrupt failure of function or complete physical
         exhaustion; "the commander's prostration demoralized his
         men" [syn: collapse, prostration]
    2: abject submission; the emotional equivalent of prostrating
       your body
    3: the act of assuming a prostrate position