James's powder \James"'s pow`der\ (Med.) Antimonial powder, first prepared by Dr. James, ar English physician; -- called also {fever powder}. Antimonial \An`ti*mo"ni*al\, a. Of or pertaining to antimony. -- n. (Med.) A preparation or medicine containing antimony. {Antimonial powder}, a consisting of one part oxide of antimony and two parts phosphate of calcium; -- also called {James's powder}.