A commenter on the prescribe/proscribe thread writes, "To decimate is to kill one in ten," strongly suggesting that this is the only proper meaning for the term.
This is incorrect. To decimate originally meant to kill one in ten, though I wouldn't be surprised if even some ancient Romans used it loosely or figuratively. Today, the term is considerably broader. You may be annoyed by this usage; you may counsel cautious writers against it (as I do in my Academic Legal Writing book); but I know of no sensible definition of "incorrect" under which the usage is incorrect, and of no sensible definition of "is" under which "To decimate" is only "to kill one in ten."
Of course, the same applies in lots of other cases. Journal comes from the word for "day," but today also means "periodical," including periodicals published at much longer intervals (e.g., the Yale Law Journal). Vaccine comes from "vaccinia," the name for cowpox (which was used to inoculate people against smallpox), but today you can have vaccines against other diseases that are made from things other than cowpox. Etymology is interesting -- but it's not the same as meaning.