WordNet sense 1 (a sect of Orthodox Jews that arose out of a pietistic movement originating in eastern Europe in the second half of the 18th century; a sect that follows the Mosaic law strictly):

Chasidim, Chassidim, Hasidim, Hassidim

WordNet sense 2 (beliefs and practices of a sect of Orthodox Jews):

Chasidism, Chassidism, Hassidism