affusion

n. pouring on of water for ritual purposes (as in baptism)

Affusion is a method of Christian baptism where water is poured on the head of the person being baptized. The word "affusion" comes from the Latin affusio, meaning "to pour on" . Affusion is one of three methods of baptism, in addition to total immersion and sprinkling, used by Christians. Christian denominations that baptize by affusion do not typically deny the legitimacy of baptizing by immersion or aspersion. Rather, they hold the more modest view that affusion is a legitimate, if not preferable, method of baptism.
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Noun
1. the act of baptizing someone by pouring water on their head
(hypernym) baptism

n. affusion, pouring on of water for ritual purposes (as in baptism)

(n.)
The act of pouring water or other fluid on the whole or a part of the body, as a remedy in disease.
  

(n.)
The act of pouring upon, or sprinkling with a liquid, as water upon a child in baptism.