There are secular definitors, who have a limited amount of oversight over a part of a diocese, and also definitors in religious orders who generally provide counsel and assistance to the superiors general and provincial superiors of their order.
In a deanery or vicarate forane, which is a grouping of several neighboring parishes within a diocese, a definitor is either the second (and unique) highest office, immediately below the dean or vicar forane and his deputy, or is the priest in charge of any of a number of even smaller districts within the deanery, called definitio.
They oversee the ecclesiastical property and generally assist the dean, under the ordinary authority of the bishop.
In the Cistercian Order, the Abbot General is assisted by a council of five definitors, traditionally two French-speaking, one German-speaking, one English-speaking and one Dutch-speaking.
The title Definitor General is used by the Discalced Carmelites, the Friars Minor and the Capuchins.