Sulphacid (?), n. [Sulpho- + acid.] (Chem.) An acid in which, to a greater or less extent, sulphur plays a part analogous to that of oxygen in an oxyacid; thus, thiosulphuric and sulpharsenic acids are sulphacids; -- called also sulphoacid. See the Note under Acid, n., 2.
[1913 Webster]