n pl -aries
(Law) a person bound to act for another's benefit, as a trustee in relation to his beneficiary
a. having the nature of a trust
b. of or relating to a trust or trustee
[from Latin fīdūciārius relating to something held in trust, from fīdūcia trust; see fiducial]
For example, members of a corporate board of directors hold positions of fiduciary trust. In other words, directors are accountable to the shareholders (owners) who elect them...
Source: The Free Dictionary