GNU Collaborative International Dictionary of English

Found one definition

1.       
   megakaryocyte (mĕgˌȧ‑kărˈĭ‑ṓ‑sīt) 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]