Kiruv (pronounced Kee-Roov) is a Hebrew word meaning "getting closer".
The term is usually applied to Orthodox Jewish groups which aim to get other Jews to become more religious. Kiruv organisations often use emotional experiences and powerful language to carry out their missions; some focus much more on the individual.
Many people regard these Kiruv organisations as cults, although their practice is not different from mainstream Orthodox Judaism.
It is probably easiest to regard them as Jewish missionaries who only target people who are already Jewish.