From Longman Dictionary of Contemporary Englishmouldermoul‧der British English, molder American English /ˈməʊldə $ ˈmoʊldər/ (also moulder away) verb [intransitive] DECAYto decay gradually old papers mouldering away in the attic→ See Verb table
Examples from the Corpus
moulder• I couldn't permit some one of your abilities to moulder away in a backwater.• Is there a warehouse somewhere filled with mouldering copies of Titanic?• Not only were they made to look lifeless and tormented, but they were crammed into mouldering fancy dress costumes.• Man, beast or daemon, Drachenfels lies mouldering in a filthy sepulchre. 