Source : Webster's Revised Unabridged Dictionary (1913)

Enervation \En`er*va"tion\, n. [L. enervatio: cf. F.
   ['e]nervation.]
   1. The act of weakening, or reducing strength.

   2. The state of being weakened; effeminacy. --Bacon.

Source : WordNet®

enervation
     n 1: lack of vitality; "an enervation of mind greater than any
          fatigue"
     2: serious weakening and loss of energy [syn: {debilitation}, {enfeeblement},
         {exhaustion}]