Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. faustus, a, um, adj. [for favostus, from faveo; lit., favorable; hence], of favorable or fortunate omen, fortunate, favorable, auspicious, prosperous, lucky (rare but class.; cf.: felix, fortunatus, beatus, prosperus, dexter, secundus): quae (omina) majores nostri quia valere censebant, idcirco omnibus rebus agendis: QVOD BONVM FAVSTVM FELIX FORTVNATVMQVE ESSET praefabantur, Cic. Div. 1, 45, 102: so, ut nobis haec habitatio Bona, fausta, felix fortunataque eveniat, Plaut. Trin. 1, 2, 3: utile sit faustumque precor, quod imagine somni Vidimus, Ov. F. 3, 27: omen, Liv. 7, 25, 11; Ov. M. 6, 448; 9, 785 al.; cf.: exitus ut classi felix faustusque daretur, Lucr. 1, 100: i pede fausto, Hor. Ep. 2, 2, 37: indoles Nutrita faustis sub penetralibus, id. C. 4, 4, 26: o faustum et felicem hunc diem! Ter. And. 5, 4, 53; cf. Cic. Tusc. 1, 49, 118: o nox illa fausta huic urbi! id. Flacc. 41, 103: annus, Ov. F. 1, 63: nisi tempestas indulget tempore fausto, favorable, suitable, Lucr. 1, 805.
Hence, * fauste, adv., favorably, fortunately: ut eis quoque hominibus ea res fauste, feliciter prospereque eveniret, Cic. Mur. 1, 1.