Lewis & Short

ūnĭvĭra (ūnĭvĭrĭa, Treb. XXX. Tyrann. 32; Inscr. Grut. 307, 3), ae, f. [unusvir], a woman that has had only one husband (post-class.), Tert. Exhort. ad Castit. 13; Hier. adv. Jovin. 1, 11.
Adj.: univira viduitas, Tert. adv. Psych. 8.