Lewis & Short

tranquillus, a. um. adj., quiet, calm, still, tranquil, opp. to motion or excitement (syn. serenus).

  1. I. Lit., chiefly of calmness of weather: ut mare, quod suā naturā tranquillum sit, ventorum vi agitari atque turbari, Cic. Clu. 49, 138: tranquillo mari gubernare, Liv. 24, 8, 12; 38, 10, 5; 28, 17. 12: leni ac tranquillo mari, Curt. 4, 2, 8: aequora, Val. Fl. 2, 609: aquae, Ov. P. 2, 7, 8: caelum, calm, tranquil, Plin. 2, 79, 81, § 192; cf. dies, id. 2, 45, 44, § 114: serenitas, Liv. 2, 62, 2: sic tranquillum mare dicitur, cum leviter movetur neque in unam partem inclinatur … scito illud non stare, sed succuti leviter et dici tranquillum, quia neque huc neque illo impetum faciat, Sen. Q. N. 5, 1, 1.
        1. b. Subst.: tranquillum, i, n., a calm; a quiet sea: tranquillum est, Alcedonia sunt circum forum, Plaut. Cas. prol. 26; cf.: qui te ad scopulum e tranquillo auferat, Ter. Phorm. 4, 4, 8: in tranquillo tempestatem adversam optare dementis est, Cic. Off. 1, 24, 83: ita aut tranquillum aut procellae in vobis sunt, Liv. 28, 27, 11: tranquillo pervectus Chalcidem, on the calm, tranquil sea, Liv. 31, 23, 4: classicique milites tranquillo in altum evecti, id. 26, 51, 6: non tranquillo navigamus, id. 24, 8, 13 Weissenb. ad loc.; cf.: tranquillo, ut aiunt, quilibet gubernator est, Sen. Ep. 85, 30: alia tranquillo velut oscitatio, Plin. 9, 7, 6, § 18.
          Plur.: testudines eminente dorso per tranquilla fluitantes, Plin. 9, 10, 12, § 35: immoti jacent tranquilla pelagi, Sen. Troad. 200.
    1. B. Transf.: tranquilla et serena frons, calm, not disturbed, Cic. Tusc. 3, 15, 31: tranquillo serenoque vultu, Suet. Aug. 79.
  2. II. Trop., calm, quiet, peaceful, placid, composed, untroubled, undisturbed, serene, tranquil (cf. quietus): efficiendum est, ut appetitus sint tranquilli atque omni perturbatione animi careant, Cic. Off. 1, 29, 102: tranquillum facere ex irato, Plaut. Cist. 3, 21; so (opp. irata) id. Poen. 1, 2, 145: locus, id. Ep. 3, 4, 8: ut liqueant omnia et tranquilla sint, id. Most. 2, 1, 70: tranquillam concinna viam, id. Stich. 2, 1, 13: placata, tranquilla, quieta, beata vita, Cic. Fin. 1, 21, 71; cf.: pacatae tranquillaeque civitates, id. de Or. 1, 8, 30: nihil quieti videre, nihil tranquilli, id. Fin. 1, 18, 38: tutae tranquillaeque res omnes, Sall. C. 16, 5; so, res, Liv. 38, 28, 1: tranquillo animo esse potest nemo, Cic. Sen. 20, 74; cf.: tranquillo pectore vultuque sereno, Lucr. 3, 294: senectus, Hor. S. 2, 1, 57: otia sine armis, Luc. 2, 266: pax, id. 1, 171.
    Comp.: ita hanc canem faciam tibi oleo tranquilliorem, Plaut. Poen. 5, 4, 66: tranquilliorem plebem fecerunt, Liv. 2, 63, 3: esse tranquillior animo, Cic. Fam. 4, 5, 6.
    Of an orator: in transferendis faciendisque verbis tranquillior (Isocrates), Cic. Or. 52, 176.
    Sup.: illud meum turbulentissimum tempus profectionis tuo tranquillissimo praestat, Cic. Pis. 15, 33: cetera videntur esse tranquilla: tranquillissimus autem animus meus, id. Att. 7, 7, 4: tranquillissima res, Ter. And. 3, 5, 14: otium, Plin. Ep. 7, 25, 2.
        1. b. Subst.: tranquillum, i, n., calmness, quiet, tranquillity, etc.: vitam … in tam tranquillo … locare, Lucr. 5, 12; cf.: esse in tranquillo, Ter. Eun. 5 (8), 9, 8: in urbe ex tranquillo nec opinata moles discordiarum … exorta est, Liv. 4, 43, 3: seditionem in tranquillum conferre, Plaut. Am. 1, 2, 16: republicā in tranquillum redactā, Liv. 3, 40, 11.
          Plur.: tranquilla tuens nec fronte timendus, Val. Fl. 1, 38.
          Hence, adv., in two forms.
      1. 1. tranquillē, calmly, quietly, tranquilly: inclamare, Plaut. Cist. 1, 1, 112: tranquille placideque, Cic. Tusc. 3, 11, 25: dicere, with leniter, definite, etc., id. Or. 28, 99.
        Comp.: tranquillius manere, Sen. Ep. 71, 15.
        Sup.: tranquillissime senuit, Suet. Aug. 2 med.
      2. 2. tranquillō, quietly, without disturbance (very rare): nec cetera modo tribuni tranquillo peregere, Liv. 3, 14, 6; cf. supra, I. b.
    1. B. Transf., tranquillizing, bringing peaceful news: tranquillae tuae quidem litterae, Cic. Att. 14, 3, 1.