As used in this subchapter:
(1) “Trust” means any express trust, with additions thereto, wherever and however created, or any separate share of a trust and includes any arrangement other than an estate which, although not a trust, has substantially the same effect as a trust; and
(2) “Trustee” means an original, additional, or successor trustee of an inter vivos or testamentary trust, whether or not appointed or confirmed by a court, and, in the case of an arrangement which is not an estate or a trust but which has substantially the same effect as a trust, the person in actual or constructive possession of the property subject to the arrangement.