Unimplemented is a word that refers to something that has not been put into action, executed or carried out. In case you want to express the same idea but also want to have a variety of choices to pick from, here are some synonymous expressions you can use: not executed, not implemented, not enacted, not applied, unfulfilled, not brought to fruition, not brought into being, not completed, not realized, unrealized, incomplete, unfinished, inoperative, dormant, inactive, idle, and unfulfilled among others. Depending on the context, you can choose the one that best fits your purpose.