interregent

From inter- +‎ regent.

interregent (plural interregents)

1. (obsolete) A person who holds royal functions during an interregnum; an interim regent.
   • 1659, T[itus] Livius [i.e., Livy], “(please specify the book number)”, in Philemon Holland, transl., The Romane Historie […], London: […] W. Hunt, for George Sawbridge, […], →OCLC:

     The Interregent [interrex] having called a generall parliament

• “interregent”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.