adv. [f. prec. + -LY2.] In an authoritative way or manner, with authority exercised or possessed; on due or good authority.
1621. Bp. Mountagu, Diatribæ, 119. They have had [to do with tithes] … but not either primarily or authoritatively.
1647. Power of Keys, ii. 6. Authoritatively he gave him the keyes.
1808. Bentham, Sc. Ref., 7. An authoritatively reported example.
1855. Milman, Lat. Chr. (1864), V. IX. viii. 452, note. The Council of Lateran … first authoritatively proclaimed transubstantiation.
1860. Froude, Hist. Eng., V. xxiv. 36. Entitled to speak authoritatively.
