c. 1600, "dictatorial" (a sense now restricted to authoritarian), from Medieval Latin authoritativus (see authority). Meaning "possessing authority" is recorded from 1650s; that of "proceeding from proper authority" is from 1809. Related: Authoritatively; authoritativeness.
1. The first authoritative study of polio was published in 1840.
2. "Very well," I said, adopting a crisp authoritative tone.
3. He has a commanding presence and deep, authoritative voice.
4. The evidence she uses is usually highly authoritative.