D defs.my
Entry 1 sense Webster, 1913

De rigueur

/dē rĭg-yo͞or'/ · De ri·gueur · IPA /də ɹɪˈɡɝ/
01 According to strictness (of etiquette, rule, or the like); obligatory; strictly required.
  1. 1.
    According to strictness (of etiquette, rule, or the like); obligatory; strictly required.