Source : Webster's Revised Unabridged Dictionary (1913)

Enfeeble \En*fee"ble\, v. t. [imp. & p. p. {Enfeebled}; p. pr. &
   vb. n. {Enfeebling}.] [OF. enfeblir, enfeiblir; pref. en- (L.
   in) + feble, F. faible, feeble. See {Feeble}.]
   To make feeble; to deprive of strength; to reduce the
   strength or force of; to weaken; to debilitate.

         Enfeebled by scanty subsistence and excessive toil.
                                                  --Prescott.

   Syn: To weaken; debilitate; enervate.

Source : WordNet®

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