a statement reported as truth that has, in fact, never been verified
a statement that seems somewhat credible but is, in fact, inaccurate and misleading; factoids are a favorite weapon of activists because by repeating the statements often, their very familiarity may make them seem credible.
An invented fact that is taken to be true because of its appearance in print. Through persistent misuse, a new meaning is taking over: a brief news item that is factual but usually trivial. Either avoid the word or be sure to convey which meaning is intended.
Factoid can refer to a spurious (unverified, incorrect, or invented) "fact" intended to create or prolong public exposure or to manipulate public opinion. It appears in the Oxford English Dictionary as "something which becomes accepted as fact, although it may not be true", namely a speculation or an assumption. The term was coined by Norman Mailer in his 1973 biography of Marilyn Monroe.