noun
: either of two chlorides of antimony:
a. : the trichloride SbCl 3 obtained as a colorless hygroscopic caustic crystalline solid from antimony and chlorine and used chiefly in coloring metals (as iron, zinc), as a catalyst, and as a mordant — called also butter of antimony
b. : the pentachloride SbCl 5 obtained as a colorless to reddish yellow caustic oily liquid with an offensive odor and used chiefly as a chlorine carrier in organic synthesis and as a catalyst