Lewis & Short

ōrātōrĭus, a, um, adj. [orator].

  1. I. Of or belonging to an orator, oratorical (class.), Cic. de Or. 1, 54, 231: ornamenta, id. Brut. 75, 261: vis dicendi, id. Ac. 1, 8, 32: ars, Quint. praef. § 17: gestus, id. 11, 3, 125: compositio, id. 1, 8, 13: virtus, id. 3, 1, 10; 6, 3, 39: ingenium, Cic. Brut. 29, 110.
    1. B. Subst.: ōrātōrĭa, ae, f. (sc. ars), the oratorical art, oratory, Quint. 2, 14, 1; 2.
  2. II. Of or belonging to praying; hence, subst.: ōrātōrĭum, ii. n. (sc. templum), a place of prayer, an oratory (eccl. Lat.): in oratorio nemo aliquid agat, nisi, etc., Aug. Ep. 109: Judith ingressa est oratorium, Vulg. Judith, 9, 1.
    Hence, adv.: ōrā-tōrĭē, oratorically (class.): pulchre, et oratorie dicere, Cic. Or. 68, 227: loqui, Auct. Her. 4, 56, 69: Quint. 9, 1, 13; opp. to tragice, comice, Sen. Ep. 100, 10.