separation of church and state

Definition from Nolo’s Plain-English Law Dictionary

A phrase most famously used by Supreme Court Justice Black in the case of Everson v. Board of Education. In discussing the Establishment Clause of the First Amendment, Justice Black said that the clause erected a "wall of separation between church and state." He explained that this means, among other things, that the government cannot participate in the affairs of a religious group, set up a church, aid or prefer one religion over another, or aid or prefer religion over nonreligion.

Definition provided by Nolo’s Plain-English Law Dictionary.