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?
So fascism is the mask of humanity falling from capital
Yes, the mask is a convenience that creates more efficient extraction of labour from workers because a willing exploitation relationship pays more and kills off less of the labour pool. The fascist method of extraction is very efficient at extreme violence to its own detriment because they'll kill off vast swathes of potential labour that could be effectively put to work. Fascist mines starved their jewish and soviet workers, starving people don't do good work and dead workers don't do any work. It's just a shit an inefficient method of exploitation really, a willing method with well fed workers is much better. The one that looks more humane is also just more efficient. They build the lie of liberalism and being humane around it out of convenience, they would build a completely different lie given different conditions.