Please just delete this or reduce it to a pointer to the Wiktionary article  There is already a wiktionary entry with more accurate usage information  In particular   Dictionaries list both meanings so its meaningless to say that  is correct by the dictionary defintion  True it follows the etymology more closely but the fact on the ground is that the meaning has changed  This happens  If there are any good attestations to support usage  please provide them  Doubtless this is the reanalysis that led to the current usage but decimate doesnt seem to be widely used in this precise sense  Usage  is current with  generally restricted to contexts where the reader is expected to be familiar with the original sense eg historical accounts  For more discussion see the Wiktionary entry its discussion and  my discussion page on Wiktionary