The Collaborative International Dictionary of English v.0.48:

Inoculation \In*oc"u*la"tion\, n. [L. inoculatio: cf. F.
   inoculation.]
   1. The act or art of inoculating trees or plants.
      [1913 Webster]

   2. (Med.) The act or practice of communicating a disease to a
      person in health, by inserting contagious matter in his
      skin or flesh, usually for the purpose of inducing
      immunity to the disease.
      [1913 Webster +PJC]

   Note: The use was formerly limited to the intentional
         communication of the smallpox, but is now extended to
         include any similar introduction of modified virus; as,
         the inoculation of rabies by Pasteur. The organisms
         inoculated are usually an attentuated form of the
         disease-causing organism, which may multiply harmlessly
         in the body of the host, but induce immunity to the
         more virulent forms of the organism.
         [1913 Webster +PJC]

   3. Fig.: The communication of principles, especially false
      principles, to the mind.
      [1913 Webster]

   4. (Microbiology) The introduction of microorganisms into a
      growth medium, to cause the growth and multiplication of
      the microorganisms.
      [PJC]

WordNet (r) 3.0 (2006):

inoculation
    n 1: taking a vaccine as a precaution against contracting a
         disease [syn: inoculation, vaccination]