Antidisestablishmentarianism is a political philosophy that is opposed to the separation of church and state. The term originated in the context of the nineteenth century Church of England, where theocratic "antidisestablishmentarians" were opposed to proposals to remove its status as the state church of England. Antidisestablishmentarianism succeeded in England, but failed in Ireland and Wales, with the Church of Ireland being disestablished in 1871 and the Church in Wales in 1920. The term has largely fallen into disuse, although the issue itself is still current (see Act of Settlement).
Antidisestablishmentarianism is often quoted as one of the longest English words that has an actual meaning (as opposed to words that were made up for the purpose of being long) — see Longest word in the English language—although there is a longer word that falls in the same category: Pseudoantidisestablishmentarianism, meaning 'false opposition to the separation of the state and the church.' Antidisestablishmentarianism could also be prefixed with any of various formative prefixes: contra-, neo-, etc., one after another, yielding perhaps a monstrosity such as contra-neo-pseudo-anti-dis-establish-ment-ari-an-ism.