\Half" blood`\ 1. The relation between persons born of the same father or of the same mother, but not of both; as, a brother or sister of the half blood. See {Blood}, n., 2 and 4. 2. A person so related to another. 3. A person whose father and mother are of different races; a half-breed. Note: In the 2d and 3d senses usually with a hyphen.