known UK /nəʊn/US /noʊn/adjective 2noun 2forms 3 adjective2 •Identified as a specific type; famous, renowned.He was a known pickpocket. •Accepted, familiar, researched.At the time, Einstein's theory was unknown to most other scientists. noun2 •Any fact or situation which is known or familiar.You have to tell the knowns from the unknowns. •A constant or variable the value of which is already determined. formsknowns · better known · best known