The Collaborative International Dictionary of English v.0.48:

Epigenesis \Ep`i*gen"e*sis\, n. [Pref. epi- + genesis.] (Biol.)
   The theory of generation which holds that the germ is created
   entirely new, not merely expanded, by the procreative power
   of the parents. It is opposed to the theory of evolution,
   also to syngenesis.
   [1913 Webster]

WordNet (r) 3.0 (2006):

epigenesis
    n 1: a geological change in the mineral content of rock after
         the rock has formed