Umberto Eco was born in 1932, in Fascist Italy. He lived the first 13 years of his life under Fascism. In 1995, he published an essay in The New York Review of Books in which he attempted to clarify the meaning of meaning of "fascism:"
Fascism became an all-purpose term because one can eliminate from a fascist regime one or more features, and it will still be recognizable as fascist. Take away imperialism from fascism and you still have Franco and Salazar. Take away colonialism and you still have the Balkan fascism of the Ustashes. Add to the Italian fascism a radical anti-capitalism (which never much fascinated Mussolini) and you have Ezra Pound.
I think it is possible to outline a list of features that are typical of what I would like to call Ur-Fascism, or Eternal Fascism. These features cannot be organized into a system; many of them contradict each other, and are also typical of other kinds of despotism or fanaticism. But it is enough that one of them be present to allow fascism to coagulate around it.
It's a long discursive essay, of more than 5,000 words, in which Eco wanders from personal reflections to political and philosophichal analysis. The core of the essay is a list of 14 features which Eco believes to be the underlying characteristics of fascism. I have condensed these 14 features into brief slides. If you watch it on auto-play, it takes 3 minutes and 45 seconds.