Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
dēcĭdŭus, a, um, adj. [1. decĭdo], falling down or off, deciduous (chiefly in Pliny: folia, Laber. ap. Non. 100, 10; Plin. 18, 25, 60, § 226; 16, 24, 38, § 92 (where Freund assumes decīdua, cut off, cf. Cato R. R. 5, 7, but without necessity): (ignes) decidui ad terras fulminum nomen habent, Plin. 2, 20, 18, § 82: sidera, falling, shooting stars, id. 2, 8, 6, § 28: cornua cervis, id. 11, 37, 45, § 127: testes pecori ad crura decidui, subus annexi, id. 11, 49, 110, § 263: dentes, id. 8, 3, 4, § 7.