Source : Webster's Revised Unabridged Dictionary (1913)

Affusion \Af*fu"sion\ ([a^]f*f[=u]"zh[u^]n), n. [Cf. F.
   affusion.]
   The act of pouring upon, or sprinkling with a liquid, as
   water upon a child in baptism. Specifically: (Med) The act of
   pouring water or other fluid on the whole or a part of the
   body, as a remedy in disease. --Dunglison.

Source : WordNet®

affusion
     n : the act of baptizing someone by pouring water on their head