nucleus
n 1: a part of the cell containing DNA and RNA and responsible
for growth and reproduction [syn: {cell nucleus}]
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