microsome

from WordNet (r) 3.0 (2006)

microsome
    n 1: a tiny granule in the cytoplasm that is where protein
         synthesis takes place under the direction of mRNA

from The Collaborative International Dictionary of English v.0.48

microsome \microsome\ n. (Cell biology)
   a tiny granule in the cytoplasm of a cell; it consists of
   ribosomes bound to fragments of the endoplasmic reticulum and
   mitochondria.
   [WordNet 1.5 +PJC]