platelet: a little plate or sclerite of chitin in a membrane.
platelet plate·let (plāt'lĭt)
A minute, irregularly shaped, disklike cytoplasmic body found in blood plasma that promotes blood clotting and has no definite nucleus, no DNA, and no hemoglobin. Also called blood platelet, thrombocyte.
Any of the numerous small, round cell fragments found in the blood of mammals that function in the clotting of blood. Platelets contain no nuclei and are formed in the bone marrow from precursor cells called megakaryocytes. Platelets contribute to the coagulation process by adhering to damaged blood vessels, fibrinogen, and other platelets. An inadequate number of platelets leads to uncontrolled bleeding.