A rumor (American English) or rumour (British English; see spelling differences) is "a tall tale of explanations of events circulating from person to person and pertaining to an object, event, or issue in public concern."
In the social sciences, a rumor involves some kind of a statement whose veracity is not quickly or ever confirmed. In addition, some scholars have identified rumor as a subset of propaganda. Sociology, psychology, and communication studies have widely varying definitions of rumor.
Rumors are also often discussed with regard to "misinformation" and "disinformation" (the former often seen as simply false and the latter seen as deliberately false, though usually from a government source given to the media or a foreign government). Rumors thus have often been viewed as particular forms of other communication concepts.
French and German social science research on rumor locates the modern scholarly definition of it to the pioneering work of the German William Stern in 1902. Stern experimented on rumor involving a "chain of subjects" who passed a story from "mouth to ear" without the right to repeat or explain it. He found that the story was shortened and changed by the time it reached the end of the chain. His student was another pioneer in the field, Gordon Allport.
The experiment is similar to the children's game Chinese whispers.
"A Psychology of Rumor" was published by Robert Knapp in 1944, in which he reports on his analysis of over one thousand rumors during World War II that were printed in the Boston Herald's "Rumor Clinic" Column. He defines rumor as
a proposition for belief of topical reference disseminated without official verification. So formidably defined, rumor is but a special case of informal social communications, including myth, legend, and current humor. From myth and legend it is distinguished by its emphasis on the topical. Where humor is designed to provoke laughter, rumor begs for belief.