The Collaborative International Dictionary of English v.0.48:

activation \activation\ n.
   1. the process of making active.

   Syn: energizing, activating
        [WordNet 1.5

   2. making active and effective (as a bomb).
      [1913 Webster]

   Note: certain devices, as bombs or artillery shells, are
         designed to be unable to operate until a specific
         action (activation or arming) is taken to make them
         operable.
         [WordNet 1.5]

WordNet (r) 3.0 (2006):

activation
    n 1: stimulation of activity in an organism or chemical [ant:
         inactivation]
    2: the activity of causing to have energy and be active [syn:
       energizing, activating, activation]
    3: making active and effective (as a bomb) [ant: deactivation,
       defusing]