Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
inter-lūnis, e, adj. [luna], at new moon, interlunar (post-class.): nox, Amm. 19, 6, 7.
interlūnĭum, ĭi, n. [interlunis], the new moon, time of new moon, interlunary interval, Plin. 18, 32, 75, § 324; 7, 5, 4, § 38.
In plur., Hor. C. 1, 25, 11.