Noun
antidisestablishmentarianism (usually uncountable, plural antidisestablishmentarianisms)
A political philosophy opposed to the separation of a religious group (church) and a government (state), especially the belief held by those in 19th-century England opposed to separating the Anglican church from the civil government or to refer to separation of church and state. [from 20th c.]
Antonym: disestablishmentarianism
Antidisestablishmentarianism is the longest common example of a word formed by agglutinative construction. Source: Internet