*megakaryocyt*

pos>n. (Anat.) A large bone marrow cell not usually found in the circulating blood; it is regarded as the precursors of blood platelets; it is up to 100 μm in diameter, with a polyploid nucleus. Also referred to as megacaryocyte, megalokaryocyte, and thromboblast. [ WordNet 1.5 +PJC ]