in ‧ ter ‧ reg ‧ num /ˌɪntəˈreɡnəm/ BrE AmE noun ( plural interregnums or interregna /-nə/) [countable] formal
[ Date: 1500-1600 ; Language: Latin ; Origin: regnum 'period of rule' ]
a period of time when a country or organization has no ruler or leader, and they are waiting for a new one