Lewis & Short

ceu, adv. [contr. from ce-ve, like neu and seu, from neve and sive], a particle of equality or comparison,

  1. I. as, like as, just as (in the ante-Aug. per., peculiar to more elevated poetry; later also in prose, in Seneca and Suet., and esp. freq. in Plin. H. N.): pars vertere terga, ceu quondam petiere rates, Verg. A. 6, 492: ceu talpae, Plin. 9, 6, 7, § 17: ceu notamus in muscis, id. 11, 48, 108, § 258; so id. 9, 37, 61, § 132; Suet. Vit. 17; Plin. 19, 12, 62, § 187.
  2. II. In poet. comparisons (hence, haud aliter follows in a corresponding clause, Verg. A. 9, 797; 10, 360, or sic, id. ib. 10, 729), like, as, like as: tenuis fugit ceu fumus in auras, Verg. A. 5, 740; so id. G. 3, 542; * Cat. 64, 239: Hecuba et natae … Praecipites atrā ceu tempestate columbae, … sedebant, Verg. A. 2, 516; * Hor. C. 4, 4, 43: ceu nubibus arcus Mille jacit varios adverso sole colores, Verg. A. 5, 88; so id. ib. 5, 527.
        1. b. With cum, as when, Verg. G. 1, 303: 4, 96; id. A. 7, 673; 9, 30; 9, 792; 10, 97; Sen. Q. N. 6, 24, 4.
        2. c. With si (twice in Lucr.), Lucr. 4, 620; 6, 161.
    1. B. Sometimes in a conditional sense, as if, as it were, like as if, etc., Enn. ap. Non. p. 483, 2: Thesea ceu pulsae ventorum flamine nubes Aërium nivei montis liquere cacumen, Cat. 64, 239: per aperta volans, ceu liber habenis, Aequora, Verg. G. 3, 194; Plin. 2, 28, 28, § 98; 9, 37, 61, § 132; 34, 18, 54, § 175; Suet. Tib. 52; Stat. Th. 1, 320.
      Hence, with a subj.: ceu cetera nusquam Bella forent, Verg. A. 2, 438; Sil. 2, 378; Stat. S. 3, 1, 6; id. Th. 2, 417; Plin. 16, 10, 18. § 41; 31, 1, 1, § 2; 34, 6, 13, § 28 al.
    2. C. In the Nat. Hist. of Pliny sometimes ceu vero = quasi vero, in refuting another’s opinion, as if, just as if: ceu vero nesciam adversus Theophrastum scripsisse etiam feminam, Plin. praef. § 29; 7, 55, 56, § 188; 11, 39, 92, § 226; 12, 1, 5, § 11 al.; cf. upon this word, Hand, Turs. II. pp. 45-49.