interlunar

adjective

in·​ter·​lu·​nar ˌin-tər-ˈlü-nər 

variants or less commonly interlunary

ˌin-tər-ˈlü-nə-rē 

: relating to the interval between old and new moon when the moon is invisible

Word History

Etymology

probably from Middle French interlunaire, from Latin interlunium interlunar period, from inter- + luna moon — more at lunar

First Known Use

1598, in the meaning defined above