Decimate
Good $DEITY:
First example in living memory of the correct use of "decimate" in a news article.
Meru Networks has retained financial advisor Deutsche Bank to review future options for the business, as it confirmed its intention to erase “more than” 10 per cent of the global workforce amid falling sales and profits. The NASDAQ-listed WLAN maker revealed last night that according to preliminary estimates for Q4, revenues …
Historically, it did mean "to lose 1 in 10". These days, it also means "to lose a large part of", so I would say that using it in the latter sense would also be correct.
That may conflict with an older dictionary, but languages evolve with use, and the generally held view is that a dictionary is descriptive, not prescriptive. Indeed, if this wasn't the case, the OED wouldn't have to keep issuing new editions.
For extreme examples of how language changes over the centuries, try reading a Shakespeare play from the original Folio, or even one of Chaucer's Canterbury Tales in the original form.
Taken from the summary of the above blog, for those who don't want to read the whole thing:
So given that these two meanings of decimate appeared almost simultaneously, why are we so obsessed with assigning the punitive meaning to the word? A likely answer is that people are falling prey to what is known as the Etymological Fallacy, a tendency to believe that a word’s current meaning should be dictated by its roots. Unfortunately for the etymological purists, decimate comes from the Medieval Latin word decimatus, which means ‘to tithe’. The word was then assigned retrospectively to the Roman practice of punishing every tenth soldier.
So, next time you attend a symposium (etymologically, drinking partner) with someone sinister (etymologically, left-handed), and they launch into a tirade about the misuse of this word, you’ll be able to decimate their argument in no time at all.
You lean something every day, thanks Badvok :-)
PS: To tithe means to pay a portion of your income, typically a tenth, in tax, or to some other organisation (support for the local church etc).