Boris bike /ˈbɒɹɪs ˈbaɪk/ noun1 •(UK, informal) A bicycle offered for hire in London, England as part of a bike-share scheme launched in 2010.London’s blue “Boris bikes” are to be painted red under a seven-year sponsorship deal with Santander worth around £7m a year, it has been announced. — 2015 formsBoris bikes