cancer of the blood, leucaemia, leukaemia, leukemia - malignant neoplasm of blood-forming tissues; characterized by abnormal proliferation of leukocytes; one of the four major types of cancer

acute lymphoblastic leukemia, acute lymphocytic leukemia - acute leukemia characterized by proliferation of immature lymphoblast-like cells in bone marrow, lymph nodes, spleen, and blood; most common in children

acute myelocytic leukemia, acute myeloid leukemia - acute leukemia characterized by proliferation of granular leukocytes; most common in adolescents and young adults