pĕremnis — Lewis & Short
pĕremnis, e, adj.per-amnis,
I of or belonging to crossing a river; only in augural lang., peremne auspicium, and subst., pĕremne, is, n., the auspices taken by magistrates on crossing a river or a spring:
peremne dicitur auspicari, qui amnem aut aquam, quae ex sacro oritur, auspicato transit,Fest. p. 245 Müll.;
p. 250 Müll.: bella nullis auspiciis administrantur: nulla peremnia servantur, nulla ex acuminibus,Cic. N. D. 2, 3, 9; cf. id. Div. 2, 36, 77.