Lewis Short
(verb) : ex-pĭo, āvi, ātum, 1
* To make satisfaction, amends, atonement for a crime or a criminal; to purify any thing defiled with crime; to atone for, to expiate, purge by sacrifice (freq. and class.; syn.: pio, lustro, placo, paco).
* Relig. t. t.
* Lit.: SACRVM COMMISSVM QVOD NEQVE EXPIARI POTERIT, IMPIE COMMISSVM ESTO: QVOD EXPIARI POTERIT, PVBLICI SACERDOTES EXPIANTO,Cic. Leg. 2, 9, 21: scelus,Hor. C. 1, 2, 29; cf.: tua scelera di immortales in nostros milites expiaverunt,i. e. have avenged,Cic. Pis. 35, 85: in iis sine illius suffimentis expiati sumus,id. Leg. 1, 14, 40; cf.: imperatum patri, ut filium expiaret pecunia publica,Liv. 1, 26, 12: aliquem,Plaut. Most. 2, 2, 34: puerum lustralibus salivis,Pers. 2, 33: quae violata sunt, expiabuntur,Cic. Att. 1, 17, 7; cf.: expiandum forum Romanum a nefarii sceleris vestigiis,id. Rab. Perd. 4, 11; id. Phil. 1, 12, 30.
* Transf., beyond the relig. sphere.
* To atone for, make amends for, repair, make good: haec superioris aetatis exempla expiata Saturnini atque Gracchorum casibus docet,Caes. B. C. 1, 7, 5: malam potentiam servili supplicio,Tac. H. 4, 11: legatorum injurias regisque caedem,Liv. 1, 14, 3: errorem,Plin. Ep. 8, 10, 1 et saep.: incommodum virtute,Caes. B. G. 5, 52 fin.: cladem victoriis,Flor. 1, 12.
* To appease (very rare): a me etiam poenas expetistis, quibus conjuratorum manes mortuorum expiaretis,Cic. Pis. 7, 16: tutelam navis,Petr. 105: iram,Sen. Oet. 857.
Charlton T. Lewis, Charles Short, A Latin Dictionary