jesus freak

noun Informal: Usually Disparaging and Offensive.

1. a member of any of several fundamentalist groups of chiefly young people (Jesus people) originating in the early 1970s and emphasizing intense personal devotion to and study of Jesus Christ and His teachings.
2. a Christian with an intense enthusiasm for Jesus Christ and His teachings.

noun

1. informal a member of any of various Christian groups that combine a hippy communal way of life with zealous evangelicalism