Lewis & Short

rē̆trō, adv. [from re and the pronominal suffix ter, as in citro, ultro, intro, etc.].

  1. I. Lit., of place, backwards, back; on the back side, behind.
        1. a. Denoting tendency, direction, with verbs or nouns of motion: multa videbis retro repulsa revorti, Lucr. 2, 130; so very often with redire, regredi, repetere, remittere, respicere, reverti, revocare, etc., v. h. vv., and cf. Drak. ad Liv. 22, 6, 7, and 27, 28, 6: vestigia retro sequor, Verg. A. 2, 753; 9, 392; 11, 405: dare lintea retro, id. ib. 3, 686: ora retro Flectit, Ov. M. 15, 685: retro inhibitā nave, Liv. 30, 10 et saep.: iter mihi retro ad Alpes versus incidit, Cael. ap. Cic. Fam. 8, 15, 2; cf.: fugam retro spectante milite, Liv. 8, 19: fugit retro, Hor. C. 2, 11, 5: ne currente retro funis eat rotā, id. ib. 3, 10, 10: meretrix retro Perjura cedit, id. ib. 1, 35, 25: retro properare, Ov. H. 5, 31: unde ad hunc orbem redii, unde retro nemo, Sen. Herc. Oet. 48.
        2. b. Denoting rest (rare): est mihi in ultimis conclave aedibus quoddam retro, Ter. Heaut. 5, 1, 29: quid retro atque a tergo fieret, ne laboraret, Cic. Div. 1, 24, 49: perculsis nullum retro subsidium foret, Tac. H. 2, 26: retro Marsigni, etc., id. G. 43: MEMORIAM SE VIVA FECIT SIBI … CVM AEDICVLIS ANTE ET A RETRO, Inscr. Orell. 4512.
  2. II. Trop.
    1. A. Of time, back; in time back, in past times, before, formerly: et deinceps retro usque ad Romulum, Cic. Rep. 1, 37, 58; cf.: SVPER OMNES RETRO PRINCIPES FORTISSIMO IMP. CAES., etc., Inscr. Orell. 1049; and so, OMNES RETRO PRINCIPES, ib. 1098: quodcumque retro est, is past, Hor. C. 3, 29, 46: praemissa retro nobilitas, Stat. S. 1, 4, 68; Traj. ap. Plin. Ep. 10, 118 (120): cujus vim si retro quoque velimus custodire (opp. in futurum), id. ib. 10, 115 (116) fin.: meliorum retro principum ( = superiorum), Lampr. Alex. Sev. 34: cum id ab aliis retro factum recordarer, Tert. Uxor. 2, 2: Hebraei retro, qui nunc Judaei, id. Apol. 18.
    2. B. In other relations, back, behind, in return, on the contrary, on the other hand, vice versa: ab imā (voce) ad summam ac retro multi sunt gradus, Quint. 11, 3, 15: ut omnia, quae sine eā (honestate) sint, longe retro ponenda censeat, Cic. Tusc. 5, 31, 87: rursum versus retroque, id. Part. 7, 24; cf.: vide rursus retro, id. Fin. 5, 28, 83: sic omnia fatis In pejus ruere, ac retro sublapsa referri, i. e. against one’s efforts or wish, Verg. G. 1, 200; cf.: retro vivere, Sen. Ep. 122 fin.: si malum perfidia, non est fallendum. Idem retro, Quint. 5, 10, 74: fructus hominis in operis consistit et retro in fructu hominis operae sunt, Dig. 7, 7, 4; cf. ib. 46, 1, 21; 46, 3, 67 et saep.
      Note: The words containing retro in composition (except retroversus and retrorsus) are post-Aug.; they are sometimes written separately.