Dictionary.net

• One who regards the distinction of person in the Trinity as a mere distinction in the mode of divine being.

1914 - Nuttall's Standard dictionary of the English language
By Nuttall, P.Austin.

• In theol., one who views the Father, Son, and Holy Spirit as modes of being, and not as having distinct personality.

1874 - Etymological and pronouncing dictionary of the English language
By Stormonth, James, Phelp, P. H.