Londonian /lʌnˈdəʊnɪ.ən/adjective 2noun 1forms 3 adjective2 •(old-fashioned, rare) Of or relating to the city of London, England. •Of or relating to Jack London (1876–1916), American author, journalist, and social activist. noun1 •(old-fashioned, rare) A Londoner. formsLondonians · more Londonian · most Londonian