bap‧tis‧m [uncountable and countable]
a Christian religious ceremony in which someone is touched or covered with water to welcome them into the Christian faith, and sometimes to officially name them [↪ christening]
a difficult or painful first experience of something:
The campaign has been a baptism of fire.
—baptismal adjective [only before noun]
a baptismal font (=container for holding the water used at baptism)