The Collaborative International Dictionary
Fiducial edge
Fiducial \Fi*du"cial\, a. [L. fiducia trust, confidence; akin to fides faith. See Faith.]
Having faith or trust; confident; undoubting; firm. ``Fiducial reliance on the promises of God.''
--Hammond.-
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.
Fiducial line or Fiducial point (Math. & Physics.), a line or point of reference, as for setting a graduated circle or scale used for measurments.