adj. cowardly; disloyal; having abandoned an oath
adv. cowardly, like a coward
n. cowardice; disloyalty
v. to become cowardly; to abandon an oath

Ruth wah nivahriin joor!
Rage/curses to (you) cowardly mortal!
(Alduin, 000C64F1)

Draal ni fah Drem, fah grik los hind do sahlo ahrk nivahriin.
Pray not for Peace, for such is the wish of the weak and cowardly.
(Word Wall for Drem, Kyne’s Peace)

Usage is comparable to nikriin ‘cowardly’, but etymology suggests the abandonment of loyalty. May have originally meant this but grew to encompass a broader meaning.

Likely a compound of ni ‘not’ and vahriin ‘sworn’.