(noun) / a trustee; an agent who represents a principal and acts in the best interest of the principal “the executor serves as a fiduciary of the estate”
(adj) / involving trust, especially with regard to the relationship between a trustee and a beneficiary “the company has a fiduciary duty to its shareholders”
In the context of probate and estate administration in New York, a fiduciary is a personal representative of an estate appointed by the Surrogate’s Court. An executor nominated in a Last Will & Testament and subsequently appointed as executor by the Surrogate’s Court is an example of a fiduciary, as is an Administrator when the decedent left no will.
Another way of thinking about a fiduciary is: a person appointed to represent another’s interests, whether in the form of a written instrument granting such person that authority (such as a power of attorney), or by an order of the court. The term includes, but is not limited to, administrators, executors, trustees, guardians or a power of attorney.