FUD refers to the intentional or unintentional spread of worrying, vague, or false information about a project or market, whose goal or effect is to create fear among investors and trigger panic selling of assets.
Sometimes FUD is stirred up by competitors or by traders who want to buy in at a lower price. Telling FUD apart from real, data-based criticism requires checking the source of the news and comparing it against the project's actual fundamentals.