post-Christian (post-kris’chen) n. [A 20th C. back formation from Christian.] 1. Someone whom Christians would say is not a Christian, but whom non-Christians consider Christian; applied by Gary Dorrien and other scholars to Unitarian Universalism and other groups formerly considered to be liberal Christians. 2. One who tries to live according to Jesus’s teachings, but who choses to distance himself/herself from conservative or fundamentalist Christianity by refusing to be called “Christian.” 3. In certain cases, a non-theist or atheist who follows the ethical teachings of Jesus. 4. An individual who resembles Christians sociologically but who does not hold Christian theological beliefs.
adj. 1. Pertaining to or derived from the moral, religious, and/or ethical teachings of Jesus, but retaining an openess to other moral, religious, and/or ethical teachings. 2. Heretical, not adhering to traditional Christian creeds; especially including the heresies of unitarianism and universalism, which are still considered heretical by most mainstream Christians. 3. Post-modern (q.v.) interpretations of Christianity. 4. As applied to religious organizations, a group that resembles Christians sociologically, but not theologically.
Update, 14 Sept 2006 — An example of “post-Christian” used in context, from Dana MacLean Greeley, 25 Beacon Street, and Other Recollections (Boston: Beacon Press, 1971), pp. 11-12:
A question asked of Unitarians and Universalists again and again is ‘Are you Christians?’ I have spoken and written many times on this subject, but I have no simple answer to the question. Most Catholic and Protestant Christians, until fairly recently anyway, would have said that we are not Christians. Most Jews would think that we are Christians. When I told one Unitarian friend that Anglicanism’s Dean Stanley referred to Channing as ‘the morning star of the second reformation,’ my friend immediately concluded that Channing was heralding or prophseying a new era, and as Protestantism (resulting from the first Reformation) went beyond Catholicism, so the second Reformation would go beyond Protestantism; a post-Protestant, post-Christian era would begin. Numerous people believe that, or interpret Unitarianism that way. It is a plausible diagnosis, though Channing would never have thought of himself as the forerunner of a non-Christian faith. (For that matter, Jesus would never have thought of himself as the forerunner of a non-Jewish faith.)
For the record, Greeley considered himself a Christian.