noun (n)

• stimulation of activity in an organism or chemical(noun.process)

  Antonym:
  inactivation
  

  source: wordnet30
• the activity of causing to have energy and be active(noun.act)

  Synonym:
  activating, energizing
  

  source: wordnet30
• making active and effective (as a bomb)(noun.act)

  Antonym:
  deactivation, defusing
  

  source: wordnet30