Calling "gaslighting" a "psychology term" seems a bit disingenuous to me, considering that the term originated as a colloquialism derived from the name of a play[1] and couple of subsequent movie adaptations[2][3].
In 1965, twenty-eight years after the stageplay was written, writers began denominalising the film's title and using it as a verb, "gaslighting". Gaslighting, in this context, is a colloquialism that loosely means to manipulate a person or a group of people in a way similar to the way the protagonist in the play (Bella) was manipulated.
[1]: https://en.wikipedia.org/wiki/Gas_Light