Ha·sid or Has·sid also Chas·sid 
(äsĭd, ô-, hä-)
(äsĭd, ô-, hä-)n. pl. Ha·si·dim or Has·si·dim also Chas·si·dim (ä-sēdĭm, ô-, hä-)
A member of a Jewish mystic movement founded in the 18th century in eastern Europe by Baal Shem Tov that reacted against Talmudic learning and maintained that God's presence was in all of one's surroundings and that one should serve God in one's every deed and word.
[From Hebrew ḥāsîd, pious, from ḥāsad, to be kind; see ḥsd in the Appendix of Semitic roots.]
Ha·sidic adj.
Ha·sidism n.