The Collaborative International Dictionary of English v.0.48:

Enervate \E*ner"vate\, v. t. [imp. & p. p. Enervated; p. pr. &
   vb. n. Enervating.] [L. enervatus, p. p. of enervare, fr.
   enervis nerveless, weak; e out + nervus nerve. See Nerve.]
   To deprive of nerve, force, strength, or courage; to render
   feeble or impotent; to make effeminate; to impair the moral
   powers of.
   [1913 Webster]

         A man . . . enervated by licentiousness. --Macaulay.
   [1913 Webster]

         And rhyme began t' enervate poetry.      --Dryden.

   Syn: To weaken; enfeeble; unnerve; debilitate.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

enervating \enervating\ adj.
   causing the loss of strength or vigor.

   Syn: debilitative, enfeebling, weakening.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

enervating
    adj 1: causing debilitation [syn: debilitative, enervating,
           enfeebling, weakening]