bur ‧ nish /ˈbɜːnɪʃ $ ˈbɜːr-/ BrE AmE verb [transitive] formal
[ Date: 1300-1400 ; Language: Old French ; Origin: brunir 'to make brown, cause to shine' , from brun 'brown' ]
1 . to polish metal or another substance until it shines
2 . to work hard in order to improve something:
He missed no opportunity to burnish his image.
—burnished adjective