What is Plenarty?

Legal Definition
In English law. Fuliness; a state of being full. A term applied to a benefice when full or possessed by an incumbent The opposite state to a vacation or vacancy. Cowell.
-- Black's Law Dictionary
Legal Definition
Eccl. law. Signifies that a benefice is full. Vide Avoidance.
-- Bouviers Law Dictionary
Legal Definition
An occupied benefice.
-- Ballentine's Law Dictionary