Source : Webster's Revised Unabridged Dictionary (1913)

Segmentation \Seg`men*ta"tion\, n.
   The act or process of dividing into segments; specifically
   (Biol.), a self-division into segments as a result of growth;
   cell cleavage; cell multiplication; endogenous cell
   formation.

   {Segmentation cavity} (Biol.), the cavity formed by the
      arrangement of the cells in segmentation or cleavage of
      the ovum; the cavity of the blastosphere. In the gastrula
      stage, the segmentation cavity in which the mesoblast is
      formed lies between the entoblast and ectoblast. See
      Illust. of {Invagination}.

   {Segmentation nucleus} (Biol.), the body formed by fusion of
      the male and female pronucleus in an impregnated ovum. See
      the Note under {Pronucleus}.

   {Segmentation of the ovum}, or {Egg cleavage} (Biol.), the
      process by which the embryos of all the higher plants and
      animals are derived from the germ cell. In the simplest
      case, that of small ova destitute of food yolk, the ovum
      or egg divides into two similar halves or segments
      (blastomeres), each of these again divides into two, and
      so on, thus giving rise to a mass of cells (mulberry mass,
      or morula), all equal and similar, from the growth and
      development of which the future animal is to be formed.
      This constitutes regular segmentation. Quite frequently,
      however, the equality and regularity of cleavage is
      interfered with by the presence of food yolk, from which
      results unequal segmentation. See {Holoblastic},
      {Meroblastic}, {Alecithal}, {Centrolecithal},
      {Ectolecithal}, and {Ovum}.

   {Segmentation sphere} (Biol.), the blastosphere, or morula.
      See {Morula}.

Source : WordNet®

segmentation
     n 1: (embryology) the repeated division of a fertilised ovum
          [syn: {cleavage}]
     2: the act of dividing or partitioning; separation by the
        creation of a boundary that divides or keeps apart [syn: {division},
         {partition}, {partitioning}, {sectionalization}, {sectionalisation}]

Source : Free On-Line Dictionary of Computing

segmentation
     
         (Or "segmentation and reassembly", SAR) Breaking
        an arbitrary size {packet} into smaller pieces at the
        transmitter.  This may be necessary because of restrictions in
        the communications channel or to reduce {latency}.  The pieces
        are joined back together in the right order at the receiver
        ("reassembly").  Segmentation may be performed by a {router}
        when routing a packet to a network with a smaller maximum
        packet size.
     
        The term "segmentation" is used in {ATM}, in {TCP/IP}, it is
        called "fragmentation" an is performed at the {IP} layer
        before the "fragments" are passed to the {transport layer}.
     
        See for example {ATM forum} {UNI} 4.0 specification.
     
        [Better reasons?]
     
        (1999-06-14)