INTERREX
Etymology
Noun
interrex (plural interrexes or interreges)
(history) An official in Ancient Rome who acted as single head of state during the interregnum between two consulates.
(history) An equivalent regent from the death of a Polish king till the election and enthronement of his successor.
(figuratively) A similar interim ruler, CEO, etc.
Source: Wiktionary
In"ter*rex`, n.; pl. E. Interrexes, L. Interreges. Etym: [L., fr.
inter between + rex king.]
Definition: An interregent, or a regent.
Source: Webster’s Unabridged Dictionary 1913 Edition