The Collaborative International Dictionary
Rubiginous
Rubiginose \Ru*big"i*nose`\, Rubiginous \Ru*big"i*nous\, a. [L. rubiginosus, fr. rubigo, robigo, rust: cf. F. rubigineux.] (Bot.) Having the appearance or color of iron rust; rusty-looking.
Wiktionary
rubiginous
a. (alternative form of rubiginose English)