Megakaryocyte

the polyploid bone-marrow precursor of platelets, that reduplicates its DNA without cell division during thrombopoiesis (platelet formation), resulting in a large, lobulated nucleus and a cell size (with as much as 100 &micro;m diameter) a magnitude above that of erythrocytes

Description
Megakaryocytes are normally present in bone marrow, not in the circulating blood, and give rise to blood platelets. Syn megacaryocyte, megalokaryocyte, thromboblast