Final answer:
An Anabaptist is a Protestant group member who advocated for the separation of church and state and the practice of adult baptism during the Reformation.
Step-by-step explanation:
In the Reformation, a member of a Protestant group who believed in advocating for the separation of church and state and baptizing only those old enough to decide to be Christian would be known as an Anabaptist. This group emerged in the 16th century as part of the broader Protestant Reformation, which was a schism within Christianity initiated by figures like Martin Luther and John Calvin, leading to the creation of various Protestant denominations.
Anabaptists were distinct in their view that baptism should be an informed choice made by believers mature enough to understand its significance, contrasting with the Catholic practice of infant baptism. Their beliefs included not only adult baptism but also pacifism, a rejection of swearing oaths, and a community-focused interpretation of Christianity. They were often persecuted for their beliefs, which were seen as radical and threatening to the established social and religious order of their time.