Definition of authoritative adjective from the Oxford Advanced Learner's Dictionary

authoritative

adjective

ɔːˈθɒrətətɪv authoritative pronunciation American

əˈθɔːrəteɪtɪv authoritative pronunciation American

əˈθɑːrəteɪtɪv

1 showing that you expect people to obey and respect youan authoritative tone of voice2 that you can trust and respect as true and correctthe most authoritative book on the subjectauthoritatively

ɔːˈθɒrətətɪvli authoritatively pronunciation American

əˈθɔːrəteɪtɪvli authoritatively pronunciation American

əˈθɑːrəteɪtɪvli

adverb