Nucleoplasm

from WordNet (r) 3.0 (2006)

nucleoplasm
    n 1: the protoplasm that constitutes the nucleus of a cell [syn:
         {nucleoplasm}, {karyoplasm}]

from The Collaborative International Dictionary of English v.0.48

Nucleoplasm \Nu"cle*o*plasm\, n. [Nucleus + -plasm.] (Biol.)
   The matter composing the nucleus of a cell; the protoplasm of
   the nucleus; karyoplasma.
   [1913 Webster]