Instead of taking stuff away from a grave (grave robbing) you are adding to the grave site.
Usually taking the form of revenge; by having lunch sat on their grave, tossing all the empty beer cans, wrappers, and crumbs over it. Then lighting up a few smokes flicking the ash about and grinding the butt into the headstone.
To finish you can then urinate and/or take a dump on the grave, using the flowers or cards to wipe with.
Steve 'Hey dude do you feel bad you will never get your revenge on Mike for bullying you?'.
John 'Naw I spent my lunch grave slobbing his plot , so it's all good now'.