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.
an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle.
an extraordinary or unusual thing, person, or event; an exceptional example or instance.
a fool or simpleton; ninny.
an extraordinary or unusual thing, person, or event; an exceptional example or instance.
a chattering or flighty, light-headed person.
a printed punctuation mark (‽), available only in some typefaces, designed to combine the question mark (?) and the exclamation point (!), indicating a mixture of query and interjection, as after a rhetorical question.
c.1600, "dictatorial" (a sense now restricted to authoritarian), from authority (q.v.). Meaning "possessing authority" is recorded from 1650s; that of "proceeding from proper authority" is from 1809.