Nucleolus

n. small round body within a nucleus composed of protein and RNA (Biology)

In cell biology, the nucleolus (plural nucleoli) is a sub-organelle of the cell nucleus, which itself is an organelle. A main function of the nucleolus is the production and assembly of ribosome components. The nucleolus is roughly spherical, and is surrounded by a layer of condensed chromatin. No membrane separates the nucleolus from the nucleoplasm.
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Noun
1. a small round body of protein in a cell nucleus; nucleoli contain RNA and are involved in protein synthesis
(synonym) nucleole
(hypernym) organelle, cell organ
(part-holonym) nucleus, cell nucleus, karyon

(n.)
A small rounded body contained in the nucleus of a cell or a protozoan.
  

(n.)
A little nucleus.
  

The site of synthesis of rRNA within the nucleus of a eukaryotic cell.