Sentence:  I know how to make her run mad with passion that has nothing to do with books and animals. I know how to make her unpin her hair, <WSD>unsash</WSD> her gown, unhook — But he hadn't said a word, only allowed the devil's own smile to lift one corner of his mouth. 
Meaning of the word marked with <WSD> tags:  To untie the sash that holds an article of clothing.