Half blood : 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.

Half blood n. : A person so related to another.

Half blood n. : A person whose father and mother are of different races; a half-breed.

Example:


Taxonomy
IMDb, Half Blood Prince, characters, Harry Potter and the Half-Blood Prince, Harry Potter, USA, Message Boards, Photos, Hogwarts School of Witchcraft and Wizardry, Daniel Radcliffe, Bellatrix Lestrange, quotes, Reviews, David Yates, cast, actors, trailers, Michael Gambon.

Defination from the web:
... Not only was 'Half Blood Prince' my favorite book in the series, it was also one of my favorite ... Half Blood Prince' probably has the least amount of action in the series, but it is by no means boring. ...