New World Dictionary of American English:
decimate -- 1) (orig) to select by lot and kill every tenth one;
2) to destroy or kill a large part;
3) (obs) to take a tenth part of
American Heritage Dictionary of the English Language:
decimate -- 1. To destroy or kill a large part of (a group);
2. a. To inflict great destruction or damage on;
b. To reduce markedly in amount;
3. To select by lot and kill one in every ten of;
USAGE NOTE: Decimate originally referred to the killing of every tenth person, a punishment used in the Roman army for mutinous legions. Today this meaning is commonly extended to include the killing of any large proportion of a group.
Mirriam-Webster:
decimate -- 1 : to select by lot and kill every tenth man of;
2 : to exact a tax of 10 percent from;
3 a : to reduce drastically especially in number;
b : to cause great destruction or harm to;
Shall I go on? There are dozens of others, up to and including the Oxford, which, by the way, doesn't even include the archaic definition except as a footnote "more or less totally superseded" by the modern usage.
So are YOU the authority or are you simply some smarmy, smug, self-righteous word nazi who thinks he knows something nobody else does? I know full well the etymology of the word. But I also know its CURRENT usage, you know, the one that ISN'T 2,000 years out of date.
The current Merriam Webster's is simply not useful nor is the New World Dictionary. If 3 people can be shown to have used a word a certain way on the street and another has written it in something that got published once then MW and NWD will baptize that word and/or usage. It still sounds ignorant, aggressively ignorant. It is like using "they" for third person singular.People who use such words with their new street validated meanings usually have problems discussing things that require that they and their interlocutors actually know what they are talking about. It becomes feelings and emotions because that doesn't require any precision.