I / inter-rex
noun

inter-rex

gen. inter-rēgis · gender masculine · decl. 3rd
one who held the regal office between the death of one king and the election of another; a regent; interrex
one who held the regal office between the death of one king and the election of another; a regent, interrex, Liv. 1, 17; 1, 32.—
one who held the supreme power from the death or absence of the chief magistrates till the election of new ones
During the times of the republic, one who held the supreme power from the death or absence of the chief magistrates till the election of new ones: L. Flaccus interrex legem de Sulla tulit, Cic. Agr. 3, 2, 5; id. Leg. 1, 15, 42; id. Dom. 14, 38: prodere, to nominate, appoint, id. Agr. 3, 2, 5: creare, Liv. 5, 31, 8: infestam patribus plebem interreges cum accepissent, id. 7, 21.