Antidisestablishmentarianism is historically defined opposition to the removal of the Anglican church as the established Church of England. People who advocated the disestablishment of the church's official status were called disestablishmentarians, and their position was called disestablishmentarianism. Thus, opposition to this position was called antidisestablishmentarianism. In rare cases, this term might be used as a general reference to opposition to the disestablishment of something else. Most often, however, it is used as an example of a very long word, and it is sometimes claimed to be the longest non-technical word in the English language.
This word originated in the United Kingdom during the early 1800s. Disestablishmentarianism in the U.K. led to the removal of Anglican church as the Church of Ireland in 1871. Several Church of England dioceses in Wales were disestablished in 1920. Calls for the Church of England to be disestablished have persisted since then, as has the opposite position, antidisestablishmentarianism.
Opposition to the removal of any government establishment might also be referred to as antidisestablishmentarianism. This might be in reference to the removal of any official state religion, for example. This usage of "antidisestablishmentarianism," however, is most likely a way of getting attention for this position because of the unusual length of the word.
At 28 letters long, "antidisestablishmentarianism" is popularly believed to be the longest English word that is not a proper noun, is not a technical or scientific term and was not intentionally coined to be an especially long word. It does not appear in some dictionaries because its usage has become virtually nonexistent except in reference to its length. A 29-letter word that appears in some dictionaries is "floccinaucinihilipilification," which refers to estimating something as being worthless but also is almost never used except as an example of a very long word. Even longer English words usually are scientific, medical or technical terms that combine multiple root words, prefixes and suffixes.