(1) Having to do with a confidence or trust. (2) Held in trust for another.
Example:
Managers of pension funds have a fiduciary responsibility to invest funds for the sole and exclusive benefit of those who will receive the pensions.
A fiduciary relationship is one in which one person places faith in another. Stockbrokers and real-estate agents have fiduciary duties to their clients, which means that they must act in the clients' best financial interests. Similarly, members of a company's board of directors have a fiduciary responsibility to protect the financial interests of shareholders. There are legal requirements for those with fiduciary responsibility, and they can be sued for breach of fiduciary duty if they fail in their responsibilities.