The Collaborative International Dictionary of English v.0.48:

Neo-Darwinism \Ne`o-Dar"win*ism\, n.
   The theory which holds natural selection, as explained by
   Darwin, to be the chief factor in the evolution of plants and
   animals, and denies the inheritance of acquired characters;
   -- esp. opposed to Neo-Lamarckism. Weismannism is an
   example of extreme Neo-Darwinism. -- Ne`o-Dar*win"i*an, a.
   & n.
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Weismannism \Weis"mann*ism\, n. (Biol.)
   The theories and teachings in regard to heredity propounded
   by the German biologist August Weismann, esp. in regard to
   germ plasm as the basis of heredity and the impossibility of
   transmitting acquired characteristics; -- often called
   neo-Darwinism.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

neo-Darwinism
    n 1: a modern Darwinian theory that explains new species in
         terms of genetic mutations