Cistrum, a kind of ancient musical instrument used by the priests of Isis and Osiris. It is described by Spinoza as an oval form, in manner of a racket, with three sticks traversing it breadthwise; which playing freely by the agitation of the whole instrument, yielded a kind of sound which to them seemed melodious. Mr Malcom takes the sistrum to be no better than a kind of rattle. Ophelius observes, that the sistrum is found represented on several medals, and on tallifrons.

Sisymbrium, water-cresses, a genus of plants belonging to the class of tetradyamnia, and to the order of filigera; and in the natural system ranged under the 39th order, filigerae. See Botany Index.