Gaslighting is a systematic pattern of abuse by which the abuser manipulates factual information to give the victim the impression that they cannot trust their own senses. It should not be confused with discounting or minimizing, two very different forms of verbal abuse that are far more common.

A form of intimidation or psychological abuse, sometimes called Ambient Abuse where false information is presented to the victim, making them doubt their own memory, perception and quite often, their sanity. The classic example of gaslighting is to switch something around on someone that you know they're sure to notice, but then deny knowing anything about it, and to explain that they "must be imagining things" when they challenge these changes.

A more psychological definition of gaslighting is "an increasing frequency of systematically withholding factual information from, and/or providing false information to, the victim - having the gradual effect of making them anxious, confused, and less able to trust their own memory and perception.

When a ‘significant other’ or friend stops wanting to hang with you unless they can’t find anyone else to hang with.
Some believe this terminology roots back to the operation of a gas lantern and how it can be turned down in an instant as not to waste fuel (i.e. a persons time) and then turned back up once there is insufficient natural light (i.e. there’s no one else to hang with).