Is a word that is a acronym for the English expression: "Fear of missing out".
FOMO is a feeling investors can experience when they see a instrument rise in price without themselves being invested. Such situations can then lead to fear, remorse or worries and give a great desire to be part of the same investment and rise in instrument price. When an investor has FOMO, it can quickly lead to "headless" investments. It's really important to know of this phenomenon, so that you can do more rational investments when this feeling accurs.