White blood cell (WBC) count. White blood cells protect the body against infection. If an infection develops, white blood cells attack and destroy the bacteria, virus, or other organism causing it. White blood cells are bigger than red blood cells and normally fewer in number. When a person has a bacterial infection, the number of white cells can increase dramatically. The white blood cell count shows the number of white blood cells in a sample of blood. The number of white blood cells is sometimes used to identify an infection or to monitor the body’s response to cancer treatment.
This is part of the CBC – Complete Blood Count Test.
Other definitions of WBC on the web found here.