Human Rights Watch defines "honor killings" as follows:
Honor crimes are acts of violence, usually murder, committed by male family members against female family members, who are held to have brought dishonor upon the family. A woman can be targeted by (individuals within) her family for a variety of reasons, including: refusing to enter into an arranged marriage, being the victim of a sexual assault, seeking a divorce — even from an abusive husband — or (allegedly) committing adultery. The mere perception that a woman has behaved in a way that "dishonors" her family is sufficient to trigger an attack on her life.
National Geographic: Thousands of Women Killed for Family "Honor"
Reuters: Indian village proud after double "honor killing"
TIME: Why Are Hindu Honor Killings Rising in India?
