Fear Of Missing Out
The fear that an opportunity will pass by, and you'll... miss out. The opposite of FUD.
Often a driving force behind a lot of bull runs. When a coin starts mooning it elicits FOMO in those who are not invested and pushes them to invest due to the fear of being left behind and possibly missing out on huge profits.
During the tail end of 2017 just about every single crypto assets' value was surging upwards and FOMO spread rapidly, causing more people to buy, driving the price up, and causing the spread of more FOMO.
* All terms and definitions may update as the Cryptionary improves.