Rubiginous is an adjective used to describe something that is rusty or covered in rust. However, there are other synonyms that can be used to describe something that is in a state of rust or corrosion. One synonym for rubiginous is oxidized, which refers to the process of the metal or material reacting with oxygen to create rust. Another synonym is corroded, which is used to describe something that has been affected by chemical reactions that cause damage or weakness. Other synonyms include rusty, decayed, deteriorated, weathered, and tarnished. All of these words can be used interchangeably with rubiginous to describe something that is rusty or in a state of corrosion.