in-fĭdēlis, e, adj., that cannot be relied upon, unfaithful, faithless.
I In gen. (rare but class.): si hoc sibi sument, nullam esse fidem, quae infideli data sit, Cic. Off. 3, 29, 106: Bellovaci, qui ante erant per se infideles, Caes. B. G. 7, 59: non infideles arbitrae Nox et Diana, Hor. Epod. 5, 50: obsecro, infidelior mihi ne fuas, quam ego sum tibi, Plaut. Capt. 2, 3, 83: ut ex infidelissimis (sociis) firmissimos redderem, Cic. Fam. 15, 4, 14: silex ad structuram infidelis, Plin. 36, 22, 49, § 169: infidelis recti magister est metus, Plin. Pan. 45.—
II In partic., in eccl. Lat., unbelieving , infidel : Christiani, Salv. de Gub. 5 init. —Adv.: in-fĭdēlĭter , faithlessly , perfidiously : nec me minus putarem reprehendendum, si inutiliter aliquid senatui suaserim quam si infideliter, Cic. Brut. 2, 1, 2; Vulg. Isa. 21, 2. — Sup. : infidelissime, Salv. contra Avar. 3.