Neutrophilia: More than the normal number of neutrophils, 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. The mature neutrophil has a segmented nucleus (it is called a seg or poly) while the immature neutrophil has band-shape nucleus (it is called a band). The neutrophil has a lifespan of about 3 days.
Neutrophilia may be due merely to a shift of neutrophils into the circulating blood as occurs, for example, with vigorous exercise. Shift neutrophilia is typically transient.
A true increase in neutrophil production usually reflects an infection, particularly a acute bacterial infection.