patripassian

from The Century Dictionary.

• noun A Monarchian who denied the distinction of three persons in one God, and held that there is only one divine Person, who in his eternal nature was termed the Father, but in his incarnation the Son, and who suffered in the passion as the Son. The term is said to occur first in literature in a treatise of Tertullian, about a. d. 200. Compare Sabellian.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Eccl. Hist.) One of a body of believers in the early church who denied the independent preëxistent personality of Christ, and who, accordingly, held that the Father suffered in the Son; a monarchian.