Definition & Meaning of "gaslighter"in English

What does "gaslighter" mean in slang?

The term "gaslighter" refers to a person who manipulates others by making them doubt their own memory, perception, or sense of reality. The structure comes from "gaslighting," derived from the play and film Gas Light, where a character is psychologically manipulated into questioning reality. It is used in informal and clinical-adjacent slang to describe persistent patterns of denial, distortion, or contradiction aimed at controlling or destabilizing another person's confidence in their own judgment.