Arhat (Sans.), also pronounced and written Arahat, Arhan, Rahat, etc., "the worthy one"; a perfected Arya, one exempt from reincarnation; "deserving Divine honours." This was the name first given to the Jain, and subsequently to the Buddhist holy men initiated into the esoteric mysteries. The Arhat is one who has entered the last and highest path, and is thus emancipated from rebirth.
Source: H.P.Blavatsky - The Key to Theosophy, The theosophical glossary