FOMO = Fear of Missing Out
FOMO is YOLO's more reasonable cousin. If you don't know what YOLO means, well ok, it means You Only Live Once-- AKA the modern day equivalent of carpe diem. So, that out of the way FOMO is just that thing you get when you're sitting at home on a Friday night, enjoying your life and Breaking Bad marathon, when you go on facebook and see good ol' Craig Rackowski is getting wasted with 11 hot girls, a mechanical bull, and he's apparently sponsored by Red Bull now. The worst part is: you're not even being excluded, you just chose not to go. Wow. You idiot. Now you have profound fear of missing out. Actually, you're already missing out, so maybe just go to sleep so it'll hurt less.