urban legend
noun
a modern story of obscure origin and with little or no supporting evidence that spreads spontaneously in varying forms and often has elements of humor, moralizing, or horror: Are there alligators living in the New York City sewer system, or is that just an urban legend?
Origin of urban legend
First recorded in 1970–75
Also called urban myth.
Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019