I believe that Orwell's essay on fascism [orwell.ru] is still as apt as ever. Essentially it's just a way to describe a political (or more generally, any ideological) opponent you don't like and historically been flung at just about everyone from communists to Catholics. It's a fancier way of saying "bad guy" in most cases.

http://orwell.ru/library/articles/As_I_Please/english/efasc

"It is usually assumed, for instance, that Fascism is inherently warlike, that it thrives in an atmosphere of war hysteria and can only solve its economic problems by means of war preparation or foreign conquests. But clearly this is not true of, say, Portugal or the various South American dictatorships. Or again, antisemitism is supposed to be one of the distinguishing marks of Fascism; but some Fascist movements are not antisemitic. Learned controversies, reverberating for years on end in American magazines, have not even been able to determine whether or not Fascism is a form of capitalism. But still, when we apply the term 'Fascism' to Germany or Japan or Mussolini's Italy, we know broadly what we mean. It is in internal politics that this word has lost the last vestige of meaning. For if you examine the press you will find that there is almost no set of people — certainly no political party or organized body of any kind — which has not been denounced as Fascist during the past ten years. Here I am not speaking of the verbal use of the term 'Fascist'. I am speaking of what I have seen in print. I have seen the words 'Fascist in sympathy', or 'of Fascist tendency', or just plain 'Fascist', applied in all seriousness to the following bodies of people:

Conservatives: All Conservatives, appeasers or anti-appeasers, are held to be subjectively pro-Fascist. British rule in India and the Colonies is held to be indistinguishable from Nazism. Organizations of what one might call a patriotic and traditional type are labelled crypto-Fascist or 'Fascist-minded'. Examples are the Boy Scouts, the Metropolitan Police, M.I.5, the British Legion. Key phrase: 'The public schools are breeding-grounds of Fascism'.

Nationalists: Nationalism is universally regarded as inherently Fascist, but this is held only to apply to such national movements as the speaker happens to disapprove of. Arab nationalism, Polish nationalism, Finnish nationalism, the Indian Congress Party, the Muslim League, Zionism, and the I.R.A. are all described as Fascist but not by the same people."