tiny bits of protoplasm found in vertebrate blood; essential for blood clotting
"After cutting his finger, he watched as the platelets rushed to the wound to form a clot and stop the bleeding."
A small colorless disk-shaped particle found in the blood of mammals, which plays an important role in the formation of blood clots.
"After his deep cut on the knee, Dr. Smith explained that his body needed time for platelets to rush to the wound and form a clot to stop the bleeding."