Lewis Short
dē-sŭbĭtō (by many written separately, de subito)
* Adv., on a sudden, suddenly (except once in Cic., only ante-class.), Plaut. Bac. 1, 1, 46; id. Capt. prol. 62; id. Most. 2, 1, 63; id. Stich. 5, 4, 39; Lucil., Enn., Naev., al. ap. Non. 517, 13-518, 1; Lucr. 2, 265; 3, 643; Cic. Rep. 6, 2, 2 (ap. Non. p. 517).
Charlton T. Lewis, Charles Short, A Latin Dictionary