What is "adoptionism"

n. (context Christianity English) A form of Christianity which maintains that Jesus is divine only in the sense that God the Father adopted him, either at Jesus' birth, or at his death, as opposed to the orthodox understanding of the nature of the Trinity.

Adoptionism, sometimes called dynamic monarchianism, is a nontrinitarian theological doctrine which holds that Jesus was adopted as the Son of God at his baptism, his resurrection, or his ascension. According to Epiphanius's account of the Ebionites, the group believed that Jesus was chosen on account of his sinless devotion to the will of God.

Adoptionism was declared heresy at the end of the 2nd century and was rejected by the Synods of Antioch and the First Council of Nicaea, which defined the orthodox doctrine of the Trinity and identified the man Jesus with the eternally begotten Son or Word of God in the Nicene Creed.