(a) As used in this Code section, the term:

(1) "Collusive execution" means every execution whereby the person exercising a power uses it by contrivance for his own benefit, he not being legitimately an intended beneficiary.

(2) "Illusory appointment" means an appointment whereby a nominal benefit only is given to one of a class, to all of whom a substantial benefit was intended.

(b) Equity may relieve against mistaken or defective executions, collusive executions, and illusory appointments.