Legal definition of fiduciary
Living Trusts Legal Terminology

for the purposes of estate administration: Fiduciary means a personal representative or trustee. The term includes an executor, administrator, successor personal representative, and a person performing substantially the same function.
A fiduciary shall administer a trust or estate in accordance with the terms of the trust or the will;
may administer a trust or estate by the exercise of a discretionary power of administration given to the fiduciary by the terms of the trust or the will;
A fiduciary shall administer a trust or estate impartially, based on what is fair and reasonable to all of the beneficiaries, except to the extent that the terms of the trust or the will clearly manifest an intention that the fiduciary shall or may favor one or more of the beneficiaries.

"Original fiduciary" means a fiduciary who is replaced by a substitute fiduciary or who makes a delegation of power under this part.(sec.355)