killer T cell (KIH-ler ... sel)
A type of immune cell that can kill certain cells, including foreign cells, cancer cells, and cells infected with a virus. Killer T cells can be separated from other blood cells, grown in the laboratory, and then given to a patient to kill cancer cells. A killer T cell is a type of white blood cell and a type of lymphocyte. Also called cytotoxic T cell and cytotoxic T lymphocyte.