Lewis & Short

aestus, ūs (archaic gen. aesti, Pac. 97 Rib.; rare form of nom. plur. aestuus). m. [kind. with aestas and Gr. αἴθω; v. aestas], an undulating, boiling, waving, tossing; a waving, heaving, billowy motion.

  1. I. Lit.
    1. A. Of fire; hence, in gen., fire, glow, heat (orig. in relation to its flashing up; while fervor denotes a glowing, ardor a burning, and calor a warming heat; yet it was early used for warming heat; v. the following example): nam fretus ipse anni permiscet frigus et aestum, heat and cold are blended, Lucr. 6, 364 (for which calor, id. 6, 368, 371 al.): multa aestu victa per agros, id. 5, 1104: exsuperant flammae, furit aestus ad auras, Verg. A. 2, 759: caniculae, Hor. C. 1, 17, 18; so id. Ep. 1, 8, 5: labore et aestu languidus, Sall. J. 51.
      In plur.: neque frigora neque aestus facile tolerabat, Suet. Aug. 81.
      So of midday heat: aestibus at mediis umbrosam exquirere vallem, Verg. G. 3, 331 (cf. Cic. Ac. 2, 22: ille cum aestuaret, umbram secutus est).
      And of the heat of disease (of wounds, fever, inflammation, etc.): ulceris aestus, Att. ap. Cic. Tusc. 2, 7, 19: homines aegri cum aestu febrique jactantur, Cic. Cat. 1, 13.
    2. B. The undulating, heaving motion of the sea, the swell, surge: fervet aestu pelagus, Pac. ap. Cic. de Or. 3, 39; hence, meton. for the sea in agitation, waves, billows: delphines aestum secabant, Verg. A. 8, 674: furit aestus harenis, id. ib. 1, 107: aestus totos campos inundaverant, Curt. 9, 9, 18.
      In Verg. once of the boiling up of water in a vessel: exsultant aestu latices, Aen. 7, 464.
    3. C. Esp., the periodical flux and reflux or ebb and flow of the sea, the tide (cf. Varr. L. L. 9, 19; Mel. 3, 1: aestus maris accedere et reciprocare maxime mirum, pluribus quidem modis, sed causa in sole lunāque, Plin. 2, 97, 99); Plaut. As. 1, 3, 6: quid de fretis aut de marinis aestibus dicam? quorum accessus et recessus (flow and ebb) lunae motu gubernantur, Cic. Div. 2, 14 fin.: crescens, Plin. 2, 100, 97, § 219: decedens, id. ib.: recedens, id. 2, 98, 101, § 220: secundus, in our favor, Sall. Fragm. ap. Gell. 10, 26, 2: adversus, against us, id. ap. Non. 138, 8.
  2. II. Trop.
    1. A. The passionate ferment or commotion of the mind, the fire, glow, ardor of any (even a good) passion (cf. aestuo, II. A.): et belli magnos commovit funditus aestus (genus humanum), has stirred up from their very bottom the waves of discord, Lucr. 5, 1434: civilis belli aestus, Hor. Ep. 2, 2, 47 (cf. id. C. 2, 7, 15): repente te quasi quidam aestus ingenii tui procul a terrā abripuit atque in altum abstraxit, Cic. de Or. 3, 36: hunc absorbuit aestus quidam gloriae, id. Brut. 81: stultorum regum et populorum continet aestus, Hor. Ep. 1, 2, 8: perstet et, ut pelagi, sic pectoris adjuvet aestum, the glow of love, Ov. H. 16, 25.
    2. B. A vacillating, irresolute state of mind, doubt, uncertainty, hesitation, trouble, embarrassment, anxiely: qui tibi aestus, qui error, quae tenebrae, Cic. Div. in Caecin. 14: vario fluctuat aestu, Verg. A. 12, 486: amor magno irarum fluctuat aestu, id. ib. 4, 532; cf. id. ib. 8, 19: aestus curaeque graves, Hor. S. 1, 2, 110.
    3. C. In the Epicurean philos. lang. of Lucretius, the undulatory flow or stream of atoms, atomic efflux, as the cause of perception (cf. affluo, I.): Perpetuoque fluunt certis ab rebus odores, Frigus ut a fluviis, calor ab sole, aestus ab undis Aequoris, exesor moerorum litora propter, etc., Lucr. 6, 926; and in id. 6, 1002 sq., the magnetic fluid is several times designated by aestus lapidis.