In a power of appointment, a donor-donee is a person who reserves a power of appointment. The creator of the power (the donor) is the person who can exercise the power (the donee).
Restatement (Third) of Property § 17.2(b) defines a donor-donee:
§ 17.2 TERMINOLOGY ASSOCIATED WITH A POWER OF APPOINTMENT
. . .
(b) “Donee.” The “donee” (“power holder”) is the person on whom the power of appointment was conferred or in whom the power was reserved. If the donor reserved the power in himself or herself, the donor is also the donee, and the term “Donor-Donee” is sometimes used to refer to such a person.
New York’s Trusts, Estates and Powers Law does not have a similar definition. See donee