I feel like it's a very ill-defined term in the imperial core, but also there seems to be no coherent agreement on the left. Many thinkers have different definitions that often overlap.
Lenin called fascism "capitalism in decay"
Fanon called it "colonialism at home"
Umberto Eco offers his own incoherent mess of a definition
Roger Griffin defines it as a "palingenetic ultranationalism" that imagine a mythical "rebirth" of some previous glory (Rome, the volk, MAGA), and in doing so seek the "dominance of the insiders of the ultra-nation over those outside of it."
Parenti states that fascism "offers a beguiling mix of revolutionary-sounding mass appeals and reactionary class politics", adding that if fascism means anything "it means all-out government support for business and severe repression of anti-business, pro- labour forces."
Andreas Malm adapts Griffin's definition in White Skin, Black Fuel to a "palindefenIve, palingenetic ultranationalism", etc, adding that in addition to the sense of rebirth to some mythical glory time, there is also a mythical defense of the ultra-nation from those who are defined as foreign, be they Muslims, central American refugees, judeo-bolsheviks, etc.
I find the most functionally useful definition of fascism is Parenti's: the violent oppression of the left to maintain the dominance of the ownership class. However I feel like it lacks the element of violent chauvinism against arbitrarily defined others in society. That is to say I suppose I also lack a coherent definition.
What say you comrades?
It's literally just conservatism taken to its logical endpoint. All other definitions overcomplicate things IMO - the main difference between conservatives and fascists is literally just whether or not they are letting the market enforce the bullshit hierarchy they believe in indirectly, or if they are using the military and police to do it directly (as with everything, there is a long blurry border where they're doing both).
A while ago I watched a panel about Fascism on YouTube and all the panelist were asked for a definition. I believe one of them was something like "Revolutionary Conservatism". I kinda like the simplicity of that definition.