fallax, ācis (gen. plur. fallacium, Cic. Lael. 25, 91 al.; but fallacum, Cat. 30, 4), adj. fallo, deceitful, deceptive, fallacious (class.; esp. freq. in Cic.; syn.: captiosus, fraudulentus, subdolus, dolosus, vafer, astutus, callidus): age, barbari (astrologi) vani atque fallaces: num etiam Graiorum historia mentita est? Cic. Div. 1, 19, 37: levium hominum atque fallacium, id. Lael. 25, 91; for which: facta impia fallacum hominum, Cat. 30, 4: vicinitas non assueta mendaciis, non fucosa, non fallax, non erudita artificio simulationis, Cic. Planc. 9, 22: posita fallacis imagine tauri, Ov. M. 3, 1 et saep.—Of inanim. and abstr. things: ut tamquam in herbis non fallacibus fructus appareat, Cic. Lael. 19, 68: (with fucosae) merces, id. Rab. Post. 14, 40: arva, Ov. A. A. 1, 401: siliquae, Verg. G. 1, 195: austri, id. A. 5, 850: herba veneni, id. E. 4, 24: vada, Plin. 5, 31, 34, § 128: genus tutius sed magis fallax (sc. venandi), more uncertain, id. 8, 8, 8, § 26 et saep.: spe falsa atque fallaci, Cic. Phil. 12, 2 fin.; so, spes, id. Mil. 34, 94: et captiosae interrogationes, id. Ac. 2, 15, 46: imitatio simulatioque virtutis, id. ib. 2, 46, 140: malitia est versuta et fallax nocendi ratio, id. N. D. 3, 30, 75.—Prov.: fallaces sunt rerum species, Sen. Ben. 4, 34, 1.— Comp.: fallacior undis, Ov. M. 13, 799: quid enim fallacius illis (vocibus)? id. R. Am. 687.—Sup.: oculorum fallacissimo sensu judicare, Cic. Div. 2, 43, 91.— With gen.: homines amicitiae fallaces, Tac. A. 16, 32.— With dat.: Planasia navigiis fallax, Plin. 3, 6, 12, § 80.—Hence, adv.: fallācĭter, deceitfully, fallaciously (cf.: falso, perperam): ratio hoc postulat, ne quid insidiose, ne quid simulate, ne quid fallaciter, Cic. Off. 3, 17, 68; id. Div. 1, 18, 35; id. Part. Or. 25, 90.—Sup.: fallacissime, Plin. 12, 16, 35, § 71.