(1) Literally, a lack of leukocytes in the blood. The term is generally used to indicate varieties of leukemic disease in which the leukocyte count in circulating blood is normal or even subnormal (i.e., no leukocytosis), but a few young leukocytes are observed; sometimes used more restrictedly to describe unusual instances of leukemia with no leukocytosis and no young forms in the blood. (2) Leukemic changes in bone marrow associated with a subnormal number of leukocytes in the blood.subleukemic leukemia. [G. a- priv. + leukos, white, + haima, blood]