Baptize, christen mean to make one a Christian or to admit one to a Christian communion by a ceremony in which water is poured or sprinkled on the head or in which the body is immersed in water.
Baptize is at once the precise and the general term for this ceremony because it implies both the rite and its ends, and it may be used in reference to both infants and adults.
Christen is the popular word, but for several centuries it has so emphasized the giving of a name, which is in some churches a part of the ceremony of baptism, that it now is used at times without any reference to the religious ceremony and even with reference to inanimate objects which are formally named, often with a ceremony analogous to that of baptism; thus, “the baby has not yet been christened” may mean either “not yet baptized” or “not yet named,” though both are commonly implied; a ship is christened by performing the ceremony of breaking a bottle of liquid (as champagne) against its sides while pronouncing its name.