authoritative: Meaning and Definition of

au•thor•i•ta•tive

1. having due authority; having the sanction or weight of authority: an authoritative opinion.
2. substantiated or supported by documentary evidence and accepted by most authorities in a field: an authoritative edition of Shakespeare; an authoritative treatment of a subject.
3. having an air of authority; accustomed to exercising authority; positive; peremptory; dictatorial: said with an authoritative air.