Soothfast \Sooth"fast`\, a. [Sooth + fast, that is, fast or firm with respect to truth.] Firmly fixed in, or founded upon, the thruth; true; genuine; real; also, truthful; faithful. [Archaic] -- {Sooth"fast`ness}, n. [Archaic] ``In very soothfastness.'' --Chaucer. Why do not you . . . bear leal and soothfast evidence in her behalf, as ye may with a clear conscience! --Sir W. Scott.