system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is gaslighting?
gpt
Why do you keep asking this dumb question all the time? This is like the 12th time you posted it to this sub.
  
The above would be an example of gaslighting.  
It is an attempt to convince someone that they are misremembering something, are stupid, or insane; by deliberately lying or manipulating the circumstances.  
The name comes from a film called "Gaslight" where a husband try to convince his wife that she is insane by stealing and hiding her things and re-arranging the furniture, lying, and basically doing everything he can to make her question her reality.