The action of causing someone grief in a video game.
Common in Call of Duty, Minecraft and a few other video games.
In minecraft it is using hacks to destroy something that someone has made, or just use hacks to kill them.
In COD it's using stuff like fly, forcefield, aimbot and ESPs.
Do not attempt griefing in real life, you may get hurt by the person you are griefing.
Joe: Bobby is griefing my new house!
Joe: HELP ME HE'S BREAKING MY STUFF!
Bob: Shut up I'm not where near your house you liar.
*Bob warps away*
Joe: WHERE DID HE GO!?!?!?!?
*Bob comes back*
Joe was slain by Bob.
Joe left the game.