From Wikipedia, the free encyclopedia:
Fear, uncertainty, and doubt (FUD) is a tactic of rhetoric used in sales, marketing and public relations. FUD is generally a strategic attempt to influence public perception by disseminating negative (and vague) information. An individual firm, for example, might use FUD to invite unfavorable opinions and speculation about a competitor's product; to increase the general estimation of switching costs among current customers; or to maintain leverage over a current business partner who could potentially become a rival.
The term originated to describe disinformation tactics in the computer hardware industry and has since been used more broadly.
P.S. Another meaning of the word FUD that Wikipedia mentions is: Female urination device
And in the Merriam-Webster Dictionary an older meaning
fud (n) 1913: Fuddy-duddy