Lewis & Short

rŏtundus (rŭt-), a, um, adj. [rota], wheel-shaped, i. e. round, circular, spherical, rotund (very freq. and class.; cf. teres).

  1. I. Lit.: cur ea, quae fuerint juxtim quadrata, procul sint Visa rotunda, Lucr. 4, 502; cf. Cic. Fin. 2, 12, 36: stellae globosae et rotundae, id. Rep. 6, 15, 15: mundum rotundum esse volunt, id. N. D. 1, 10, 24.
    Comp.: mundum ita tornavit, ut nihil effici possit rotundius, Cic. Univ. 6; so, bacae, Hor. Epod. 8, 13; cf.: capita rotundiora … rotundissima, Cels. 8, 1 fin.: locus infimus in rotundo, Cic. Tusc. 5, 24, 69: togae, hanging evenly all round, Quint. 11, 3, 139.
    Prov.: diruit, aedificat, mutat quadrata rotundis, i. e. turns every thing upside down, Hor. Ep. 1, 1, 100.
  2. II. Trop., round, rounded.
    1. A. In gen.: sapiens Fortis et in se ipse totus, teres atque rotundus, Hor. S. 2, 7, 86: illa rotunda et undique circumcisa, Quint. 8, 5, 27.
    2. B. In partic., of speech (opp. rough, unpolished), round, well turned, smooth, polished, elegant (in Cic. with quasi or ut ita dicam added; but v. infra, adv. b.): erat verborum et delectus elegans et apta et quasi rotunda constructio, Cic. Brut. 78, 272; cf.: Thucydides praefractior nec satis, ut ita dicam, rotundus, id. Or. 13, 40: Graiis dedit ore rotundo Musa loqui, Hor. A. P. 323; celeris ac rotunda distributio, Quint. 3, 4, 16: rotunda volubilisque sententia, Gell. 11, 13, 4: rotundi numeri (with brevis), id. 17, 20, 4: verba, id. 16, 1, 1.
      Hence, adv.: rŏtun-dē.
        1. * a. (Acc. to I.) Roundly: ut in orbem quam rotundissime formetur, Col. Arb. 5, 2.
        2. * b. (Acc. to II.) Roundly, smoothly, elegantly: a te quidem apte ac rotunde, Cic. Fin. 4, 3, 7.