Section 4A. The following words as used in this section and section four B shall, unless the context otherwise requires, have the following meanings:—

''Customer''—any resident of this commonwealth, who engages in trust business with, or enters into discussions or correspondence creating a trust business relationship with a fiduciary, or where such relationship arises from a revision or amendment of an existing trust relationship involving any material change in matters subject to disclosure under this section and section four B except in such cases where the resulting fiduciary functions are to be performed without compensation.

''Trust business''—any activity conducted by an executor of a will or codicil, an administrator with the will annexed, an administrator of the estate of any person, a guardian, a conservator, or a trustee under a will or instrument creating a trust for the care and management of property, while he is acting in such a fiduciary capacity.

''Fiduciary''—as used in this section refers to any corporation, bank, trust company or individual who charges compensation for its or his services while acting in any of the capacities set forth in the paragraph defining ''Trust Business'', and whose gross annual compensation from all such fiduciary services is in excess of twenty-five thousand dollars for each of the three next immediate preceding taxable years.

''Trust company''—any trust company incorporated in the commonwealth and any corporation or association which acts as a corporate fiduciary or trustee within the commonwealth.