1.
false rumor; hoax; misinformation
A deliberately or carelessly spread piece of false information. Abbreviated from the German word 'Demagogie' (demagoguery). In modern Japanese, it refers broadly to any false rumor or piece of misinformation, especially one spread online or through word of mouth.
Etymology
From German 'Demagogie' (demagoguery). Originally used in political contexts to describe propaganda, but the meaning has broadened to include any false rumor or misinformation.
Usage
デマ is stronger than 噂 (rumor), as it specifically implies the information is false. It has become especially common in the context of internet misinformation.