(verb) : to drive someone insane by making them doubt their perceptions or memories
"I had a couple of coworkers attempt to gaslight me once. They swore up and down that I was at a particular meeting. The meeting never happened. However, the attempted gaslighting did motivate me to find another job." comment by Mariposa on the Laurie Kendrick blog, July 5, 2008
The term comes from "Gaslight," a 1944 movie in which a husband tries to drive his wife crazy by changing minor details in their house including the brightness of the gas lights and then insisting they've always been that way.
Chris L., IA