Fi‐du″cial (?), a. [L. fiducia trust, confidence; akin to fides faith. See Faith.] 1. Having faith or trust; confident; undoubting; firm. “Fiducial reliance on the promises of God.” Hammond.
2. Having the nature of a trust; fiduciary; as, fiducial power. Spelman.
Fiducial edge(Astron. & Surv.), the straight edge of the alidade or ruler along which a straight line is to be drawn. — Fiducialline or point(Math. & Physics.), a line or point of reference, as for setting a graduated circle or scale used for measurments.