"antidisestablishmentarianism:" This word, loaded with stacked prefixes, is the longest word in the English language, as far as I am aware. The breakdown is as follows.
"Establishment" means "the way things are; the governing authorities."
So an "establishmentarian" is someone who prefers to keep the system the way it is.
Conversely, a "disestablishmentarian" is a sort of rebel; someone who works to "disestablish" the existing system.
Therefore, an "antidisestablishmentarian" is someone who works against this kind of person; someone who believes these people should be opposed.
And finally, the suffix "ism" refers to a belief or philosophy. So "antidisestablishmentarianism" is the philosophy of being an "antidisestablishmentarian."