The Collaborative International Dictionary of English v.0.48:

Innervation \In`ner*va"tion\, n. [Cf. F. innervation.]
   1. The act of innerving or stimulating.
      [1913 Webster]

   2. (Physiol.) Special activity excited in any part of the
      nervous system or in any organ of sense or motion; the
      nervous influence necessary for the maintenance of life,
      and the functions of the various organs.
      [1913 Webster]

   3. (Anat.) The distribution of nerves in an animal, or to any
      of its parts.
      [1913 Webster]

WordNet (r) 3.0 (2006):

innervation
    n 1: the neural or electrical arousal of an organ or muscle or
         gland [syn: excitation, innervation, irritation]
    2: the distribution of nerve fibers to an organ or body region