Sesquisulphide \Ses`qui*sul"phide\, n. [Sesqui- + sulphide.]
(Chem.)
A sulphide, analogous to a sesquioxide, containing three
atoms of sulphur to two of the other ingredient; -- formerly
called also {sesquisulphuret}; as, orpiment, {As2S3} is
arsenic sesquisulphide.
[1913 Webster]