De-collate refers to the act of separating the pages of a book that have been collated (ordered). It is a very specific term, but there are a few synonyms that can be used. One word that can be used as a synonym is "unorder." This word means to undo or reverse the order of something. Another synonym for de-collate is "disorder." This word refers to the act of removing or disrupting order. "Unsort" is yet another synonym that can be used for de-collate. This word refers to the act of undoing or reversing the sorting order of something. Overall, although de-collate is a very specific term, there are a few alternative words that can be used.