de ri ‧ gueur /də riːˈɡɜː $ -ˈɡɜːr/ BrE AmE adjective [not before noun]
[ Date: 1800-1900 ; Language: French ; Origin: 'of strictness' ]
considered to be necessary if you want to be accepted, fashionable etc – used humorously:
the gleaming white teeth that are de rigueur for movie stars