Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. moenĭa, ĭum (gen. plur. moeniōrum for moenium, like anciliorum for ancilium, acc. to Cledon. p. 1898 P.; abl. plur. MOENIIS for moenibus, Inscr. Grut. 408, 1, 34; in sing. moene: moene singulariter dixit Ennius (al. Naevius), Paul. ex Fest. p. 145 Müll.), n. [perh. Sanscr. root mū-, bind; Gr. ἀμύνω, μύνη; cf.: munus, immunis, munio], defensive walls, ramparts, bulwarks, city walls, as a means of protection and security.
mūnĭa (archaic form moenia: moenia praeter aedificia significant etiam et munia, hoc est officia, Paul. ex Fest. p. 151 Müll.), ōrum (class. only in the form munia, nom. and acc.), n. [Sanscr. root mū, bind; that to which one is bound; cf. Gr. ἀμύνω; also moenia, murus, munus, immunis, etc.], duties, functions, esp. official or professional duties (class.; syn.: officia, munera): munia candidatorum, Cic. Mur. 35, 73: qui suis cervicibus tanta munia atque rem publicam sustinent, id. Sest. 66, 138: cuncti omnium ordinum extrema munia sequi, Sall. Fragm. ap. Non. 137, 12: belli pacisque munia facere, Liv. 1, 42: senatūs, magistratuum, legum in se trahere, Tac. A. 1, 2; cf.: munia consulatūs obire, id. ib. 2, 26: munia ducis implere, id. H. 1, 62: vitae servare munia, Hor. Ep. 2, 2, 131.
Post-class. forms, gen.: OB HAEC INSIGNIA GENERA MVNIORVM, Inscr. Spon. Miscell. Antiq. p. 36 (A. D. 394), but gen. muniūm, Tert. Cor. Mil. 11.
Dat. munibus, Claud. Laud. Stil. 3, 76: muniis, Amm. 31, 2, 20; Serv. Verg. A. 12, 559; Cod. Just. 8, 10, 8 al.