adult baptism
noun
The christening of an adult, or one who has reached the age of discretion, especially as practised by a church or sect that maintains baptism should only be administered to believing adults (as the Anabaptists, Mennonites, etc.); opposed to infant baptism.
Origin
Mid 17th century; earliest use found in John Tombes (1602–1676), clergyman and ejected minister.