What is Advowson?

Legal Definition
Advowson (or "patronage") is the right in English law of a patron (avowee) to present to the diocesan bishop (or in some cases the ordinary if not the same person) a nominee for appointment to a vacant ecclesiastical benefice or church living, a process known as presentation (jus praesentandi, Latin: "the right of presenting"). The word derives, via French, from the Latin advocare, from vocare "to call" plus ad, "to, towards", thus a "summoning". In effect, an advowson is the right to nominate a person to be parish priest (subject to episcopal approval), and such right was often originally held by the lord of the manor of the principal manor within the parish.
-- Wikipedia
Legal Definition
Ecclesiastical law. From advow or advocare, a right of presentation to a church or benefice. He who possesses this right is called the patron or advocate, (q. v.) when there is no patron, or he neglects to exercise his right within six months, it is called a lapse, i. e. a title is given to the ordinary to collate to a church; when a presentation is made by one who has no right it is called a usurpation.

2. Advowsons are of different kinds, as Advowson appendant, when it depends upon a manor, &c. – Advowson in gross, when it belongs to a person and not to a manor. – Advowson presentative, where the patron presents to the bishop. – Advowson donative, where the king or patron puts the clerk into possession without presentation. – Advowson of the moiety of the church, where there are two several patrons and two incumbents in the same churcb. – A moiety of advowson, where two must join the presentation, of one incumbent. – Advowson of religious houses, that whicb is vested in the person who founded such a house. Techn. Dict.; 2 Bl. Com. 21; Mirehouse on Advowsons; Com. Dig. Advowson, Quare Impedit; Bac. Ab. Simony; Burn's Eccl. Law, h. t.; Cruise's Dig. Index, h. t.
-- Bouviers Law Dictionary
Legal Definition
In English ecclesiastical law. The right of presentation to a church or ecclesiastical benefice; fhe right of presenting a fit person to the bishop, to be by him admitted and instituted to a certain benefice within the diocese, which has become vacant 2 BL Comm. 21; Co. Litt. 119b, 120a. The person enjoying this right is called the "patron" (pairons) of the church, and was formerly termed "advocatus," the advocate or defender or in English, "advowee." Id.; 1 Crabb, Real Prop, p. 129, § 117. Advowsons are of the following several kinds, via.:
See also
-- Black's Law Dictionary
Legal Definition
A right of presentation to a church or benefice. See 2 Bl. Comm. 21.
-- Ballentine's Law Dictionary