NOUN (1)

1. one of a pair of small cylindrical cell organelles near the nucleus in animal cells; composed of nine triplet microtubules and form the asters during mitosis;

The Collaborative International Dictionary of English v.0.48:

centriole \centriole\ n. (Biol.)
   one of two small cylindrical cell organelles composes of nine
   triplet microtubules, which form the asters during mitosis.
   [WordNet 1.5]