authoritative

Adjective Satellite

• having authority or ascendancy or influence
  • "the captain's authoritative manner"
• of recognized authority or excellence
• sanctioned by established authority
  • "an authoritative communique"

Adj

• Arising or originating from a figure of authority
• Highly accurate or definitive; treated or worthy of treatment as a scholarly authority
• Having a commanding style.

Examples

• He instructed us in that booming, authoritative voice of his.
• The authoritative rules in this school come not from the headmaster but from the aged matron.
• This book is the world's most authoritative guide to insect breeding habits.

Synonyms

authorised, authorized, classic, classical, definitive, important, formal, grave, magisterial, masterful, of record, oracular, precise, proper, sterling