What Is Gaslighting?

A few years ago, the word wasn't used very much, but it came up in a conversation with Amber and Paul. And then after the conversation, the three of us kept noticing the word all the time. Maybe it's because that word suddenly started trending, not because we used it, but just because it was trending in the world. Imagine if I had that much influence, I was just like introducing new word and suddenly everyone's using it. But anyway, the point is that you notice a word, you kind of get to know it and suddenly you're much more able to notice it again and again and again. So, what am I saying?