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).
Unsuspecting Dupe: “Man, I don’t know what’s up with Emmy. Everything’s cool and then all of a sudden she won’t call for a couple weeks; then she’ll just start showing up again.”
Unsuspecting Dupes friend: “Yea, she’s gaslighting you bro’.”