WordWeb Online

1. Based on trust
    
2. Relating to or of the nature of a legal trust (i.e. the holding of something in trust for another)
   "fiducial power";
   - fiduciary
    
3. (physics) used as a fixed standard of reference for comparison or measurement
   "a fiducial point"

See also: straight-up [informal], trustable, trustworthy, trusty

Encyclopedia: Fiducial