Christadelphian /ˌkrɪs.təˈdɛl.fɪ.ən/adjective 1noun 1forms 1 adjective1 •Pertaining to the Christadelphians. noun1 •A member of a particular nontrinitarian Christian denomination founded in the mid-19th century.When Malone next looked round he was gone. "He is one of these Second-coming fanatics," he whispered to Enid. There are a lot of them—Christadelphians, Russellites, Bible Students and what-not. — 1925 formsChristadelphians