FUD is an acronym that stands for Fear-Uncertainty-Doubt
In the cryptocurrency and digital asset industry, spreading Fear Uncertainty and Doubt is a psychological tactic used to scare weak market participants (weak hands) into selling their positions at a loss. FUD is typically spread by mainstream media & other low moral quality industry participants.
example:
Billy bought a few bitcoins at $6,000 last year, after hodling it for a few months the FUD got to him and he sold everything at $4,400. Not even a month later Bitcoin Rallies straight past $10,000.