The Collaborative International Dictionary of English v.0.48:

Centrosome \Cen"tro*some`\, n. [Gr. ? center + -? the body.]
   (Biol.)
   A peculiar rounded body lying near the nucleus of a cell. It
   is regarded as the dynamic element by means of which the
   machinery of cell division is organized.
   [1913 Webster]

WordNet (r) 3.0 (2006):

centrosome
    n 1: small region of cytoplasm adjacent to the nucleus; contains
         the centrioles and serves to organize the microtubules
         [syn: centrosome, central body]