Medical Definition of Neutrophil. Neutrophil: A type of white blood cell, a granulocyte that is filled with microscopic granules, little sacs containing enzymes that digest microorganisms. Also known as polymorphonuclear leukocyte or poly.
Definition of Neutropenia. Neutropenia: Not enough neutrophils, neutrophils being a type of white blood cell (specifically a form of granulocyte) filled with neutrally-staining granules, tiny sacs of enzymes that help the cell to kill and digest microorganisms it has engulfed by phagocytosis.
Approved by the Cancer.Net Editorial Board, 08/2015. Neutropenia is a low level of neutrophils, a type of white blood cell. All white blood cells help the body fight infection. Neutrophils fight infection by destroying harmful bacteria and fungi or yeast that invade the body. Neutrophils are made in the bone marrow. Bone marrow is the spongy tissue found inside larger bones such as the pelvis, vertebrae, and ribs.