nucleus (
http://definr.com/nucleus)
n 1: a part of the cell containing DNA and RNA and responsible
for growth and reproduction [syn:
cell nucleus,
karyon]
2: the positively charged dense center of an atom
3: a small group of indispensable persons or things; "five
periodicals make up the core of their publishing program"
[syn:
core,
core group]
4: (astronomy) the center of the head of a comet; consists of
small solid particles of ice and frozen gas that vaporizes
on approaching the sun to form the coma and tail
5: any histologically identifiable mass of neural cell bodies
in the brain or spinal cord