Wiktionary
n. (alternative spelling of honour killing English)
WordNet
n. an ancient Muslim tradition still sometimes observed; a male member of the family kills a female relative for tarnishing the family image
Wikipedia
An honor killing or shame killing is the homicide of a member of a family by other members, due to the perpetrators' belief that the victim has brought shame or dishonor upon the family, or has violated the principles of a community or a religion, usually for reasons such as refusing to enter an arranged marriage, being in a relationship that is disapproved by their family, having sex outside marriage, becoming the victim of rape, dressing in ways which are deemed inappropriate, engaging in non-heterosexual relations or renouncing a faith.