The trash gnome is the selected person, out of a group that sits together for lunch, that throws everyone's trash away. Currently an in-joke between a few people... you know who you are.
The position of Trash Gnome should be considered as a trade-off; you have the Holy Privelege of eating lunch with us (although we hate you!) provided that you throw out all our trash.
Also known as Trash Fairy, Trash Elf, Trash Nazi.
Me: Shivam, YOU'RE the trash gnome! <a strong-handed push of the large trash can commonly found in our school>
Him: No, I don't want to be the trash gnome <push of trash can back to me> - now give me a dollar or you get ketchup all over yourself.