Lewis & Short

2. transgressus, ūs, m. [transgredior], a passing over, passage (very rare); mostly abl. sing.: auspicium prosperi transgressus, Tac. A. 6, 43 (37): vitare proelium in transgressu, Sall. Fragm. ap. Gell. 10, 26, 2 (id. H. 1, 65 Dietsch): in transgressu amnis, Tac. A. 11, 10: Euphratis, id. ib. 15, 7.