The Collaborative International Dictionary of English v.0.48:
Ferruginous \Fer*ru"gi*nous\ (f[e^]r*r[udd]"j[i^]*n[u^]s), a. [L. ferruginus, ferrugineus, fr. ferrugo, -ginis, iron rust: cf. F. ferrugineux. See Ferrugo.] 1. Partaking of iron; containing particles of iron. --Boyle. [1913 Webster] 2. Resembling iron rust in appearance or color; brownish red, or yellowish red. [1913 Webster]