authoritative

/əˈθɔrəˌteɪtɪv/
adjective
  1. Having or showing the power or right to give orders, make decisions, and enforce obedience.
    • The coach is the most authoritative person on the team when it comes to game strategy.
    • She spoke with an authoritative tone that left no room for argument.
    • The principal's authoritative voice made everyone in the hallway stop talking.
  2. Having reliable, accurate, and trustworthy knowledge; considered an expert.
    • The scientist published an authoritative study on climate change.
    • This textbook is considered the authoritative source on ancient Roman history.
    • For medical advice, it's best to consult an authoritative website like the CDC.
Antonyms
What does "authoritative" mean? | whatsthatwordmean | whatsthatwordmean