The Collaborative International Dictionary of English v.0.48:

Variolation \Va`ri*o*la"tion\, n. (Med.)
   Inoculation with smallpox.
   [1913 Webster]

WordNet (r) 3.0 (2006):

variolation
    n 1: the obsolete process of inoculating a susceptible person
         with material taken from a vesicle of a person who has
         smallpox [syn: variolation, variolization]