Entry 1 sense Webster, 1913 Affusion /(ăf*fū"zhŭn)/ · Af·fu·sion · IPA 01 n. The act of pouring upon, or sprinkling with a liquid, as water upon a child in baptism. 1. The act of pouring upon, or sprinkling with a liquid, as water upon a child in baptism.(Med.) [archaic]