The Collaborative International Dictionary of English v.0.48:

Impregnation \Im`preg*na"tion\, n. [Cf. F. impr['e]gnation, LL.
   impraegnatio.]
   1. The act of impregnating or the state of being impregnated;
      fecundation.
      [1913 Webster]

   2. (Biol.) The fusion of a female germ cell (ovum) with a
      male germ cell (in animals, a spermatozo["o]n) to form a
      single new cell endowed with the power of developing into
      a new individual; fertilization; fecundation.
      [1913 Webster]

   Note: In the broadest biological sense, impregnation, or
         sexual generation, consists simply in the coalescence
         of two similar masses of protoplasmic matter, either
         derived from different parts of the same organism or
         from two distinct organisms. From the single mass,
         which results from the fusion, or coalescence, of these
         two masses, a new organism develops.
         [1913 Webster]

   3. That with which anything is impregnated. --Derham.
      [1913 Webster]

   4. Intimate mixture; infusion; saturation.
      [1913 Webster]

   5. (Mining) An ore deposit, with indefinite boundaries,
      consisting of rock impregnated with ore. --Raymond.
      [1913 Webster]

WordNet (r) 3.0 (2006):

impregnation
    n 1: material with which something is impregnated; "the
         impregnation, whatever it was, had turned the rock blue"
    2: the process of totally saturating something with a substance;
       "the impregnation of wood with preservative"; "the saturation
       of cotton with ether" [syn: impregnation, saturation]
    3: creation by the physical union of male and female gametes; of
       sperm and ova in an animal or pollen and ovule in a plant
       [syn: fertilization, fertilisation, fecundation,
       impregnation]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "impregnation":
   absorption and regurgitation, artificial insemination,
   brainwashing, brewing, catechization, conditioning, conjugation,
   cross-fertilization, cross-pollination, decoction, dictation,
   drench, drenching, ducking, dunking, enrichment, fecundation,
   fertilization, getting with child, heterogamy, imbruement,
   imbuement, implantation, impression, inculcation, indoctrination,
   infiltration, infixation, infixion, infusion, injection,
   inoculation, insemination, instillation, instillment,
   interpenetration, isogamy, leaching, lixiviation, maceration,
   marination, orthogamy, penetration, percolation, permeation,
   pervasion, pollination, pollinization, pulping, reindoctrination,
   saturation, seething, soak, soakage, soaking, sopping, souse,
   sousing, steeping, suffusion, zygosis