The Collaborative International Dictionary of English v.0.48:

Manifestation \Man`i*fes*ta"tion\, n. [L. manifestatio: cf. F.
   manifestation.]
   1. The act of manifesting or disclosing, or the state of
      being manifested; discovery to the eye or to the
      understanding.
      [1913 Webster]

   2. That which manifests; a phenomenon which gives evidence of
      something hidden; exhibition; display; revelation; as, the
      manifestation of God's power in creation; the delayed
      manifestation of a disease.
      [1913 Webster +PJC]

            The secret manner in which acts of mercy ought to be
            performed, requires this public manifestation of
            them at the great day.                --Atterbury.
      [1913 Webster]

   3. The materialization or apparition of a spirit; -- a
      phenomenon claimed to be seen by spiritualists.
      [PJC]

WordNet (r) 3.0 (2006):

manifestation
    n 1: a clear appearance; "a manifestation of great emotion"
    2: a manifest indication of the existence or presence or nature
       of some person or thing; "a manifestation of disease"
    3: an appearance in bodily form (as of a disembodied spirit)
       [syn: materialization, materialisation, manifestation]
    4: expression without words; "tears are an expression of grief";
       "the pulse is a reflection of the heart's condition" [syn:
       expression, manifestation, reflection, reflexion]
    5: a public display of group feelings (usually of a political
       nature); "there were violent demonstrations against the war"
       [syn: demonstration, manifestation]