I don’t see “gaslighting” as being the best term here.
Steve Baker
13

You’re kind of mansplaining here with the link to the Wikipedia page about NPD and all, but I get what you’re saying. 
The original definition of gaslighting does, indeed, fit your description based on the movie. It’s a deliberate and repeated act or acts intended to force a victim to question their perception of reality. It’s intended to make the victim feel as if they’re losing their mental faculties. 
The great thing about language, though, is that it is not a static entity or law, but an ever-changing, ever-evolving agreement to assign meaning to words. As we evolve socially, we learn more about human psychology and our understanding changes. 
The use of the term ‘gaslighting’ is changing, particularly in view of what we’re learning about NPD, because it comes up so often in cases of NPD. Because it is such a useful term to describe a certain form of persistent lying, and because we don’t have an alternative term with as much power, it’s now often being used to describe intentional, semi-intentional, and unintentional attempts to force others to question their perception of reality as well as to force others to conform to a deluded abuser’s sense of reality. It’s a useful term in this larger context which is why people are expanding its meaning.
Personally, I like the expression ‘mind fuckery’, but I understand people find it rather broad.

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