The only professional journalist to become the leader of a nation, Mussolini, defined Fascism quite nicely and IMHO if you invent a word and implement the concept behind it, no one else gets to change your definition. Even though, of course, like any politician in the real world Benito had to change the practical definition somewhat.
Fascism is one-party control of the state combined with (mostly, supposedly) free markets. Harnessing Capitalism but without all the messy partisan politics. Nationalism is also a component, but the important one is using the force of markets but no competing political parties.
Fascism works quite well. Hitler’s Germany was initially Fascist and that is what helped pump up their economy before they abandoned it in favor of Nazism which is entirely different (Nazism is a racial movement, quite willing to go as socialist as necessary to work towards racial purity, economics being secondary).
Anyone mixing the two up being obviously too much of an ignoramus to take seriously about anything else.
Ignorant idiots on both right and left often use these terms to mean “Something I don’t like”, and should be ignored and reviled. Each has precise, and very different definitions to anyone who has ever cracked open a book on politics.
Communists always use “Fascist” instead of “Nazi” because to do so would be admitting they were fellow Socialists.
Look at any Soviet Propaganda from WWII, they never used the term “Nazi”, just “Fascist”.
Woody Guthrie’s Guitar said “This Machine Kills Fascists”, it didn’t say “This Machine Kills Nazis”. We didn’t really do all that much fighting against the Italians during the War.