One who has a parent of Christian descent and a parent of Jewish descent. Thus the blood of said person is contaminated by the Jewish portion of the familycreating a Mudblood.
Hermione: At least no one on the Gryffindor Team bought their way in. They got it on pure talent.
Draco: No one askedyour opinion, you filthy little Mudblood.
Ron: You'll pay for that one Malfoy, Eat Slugs!
1. what happens when you fuck a girlin the ass and pussy while she is on her period. it's called mudblood because afterward your cock will be covered in shit and blood, or, mudblood.
2. an insult from harry potter, meaning someone is half muggle and half wizard.
A mudblood is someone who is half-jewish. Because said individual is only 1/2 Jew, he or she is not pure (because only full jews are pure) so he or she is a mudblood.