It means untouchable. It is a term popularized by Gandhi and invented by Nagarazimba Metha. It is used to refer to the Dalits, the poorest and most discriminated against members of castes in India.
HARIJAN of hindustani : devanagari , nastaleeq . Term created by the Gujararí poet Nagarazimba Metha and popularized by Mohandas Gandhi to refer to the Dalit, traditionally considered untouchables.