a member of any of various Protestant sects, formed in Europe after 1520, that denied the validity of infant baptism, baptized believers only, and advocated social and economic reforms as well as the complete separation of church and state.
1530s, "one who baptizes over again," from L. anabaptismus "second baptism" (used in literal sense from 4c.), as if from Gk. ana- "up (in place or time), back again, anew" + baptismos "baptism." Originally in Eng. in ref. to sect that practiced adult baptism and arose in Germany 1521. Probably so called because, as a new faith, they baptized converts who had already been baptized (as infants) in the older Christian churches. Modern branches only baptize once (adults) and do not actively seek converts. The name also was applied, usually opprobriously, to Baptists, perhaps due to the multiple immersions of their baptisms.