Nonplussed = unfazed?

[Paul McFedries]

In today's Word Spy, I pointed out that reporter Gina Kolata of The New York
Times uses the word "nonplussed" incorrectly in the following citation:

"Yet he was nonplussed by the number of attacks on that single day last
week. 'I think it's fairly typical,' he said."

Clearly she's using it here to mean "unfazed" and I pointed out that
although this is a common error, the correct meaning is "bewildered; at a
loss." One subscriber has taken me to task on this. Calling me a
"prescriptivist" (ouch!), he said that the "unfazed" meaning is now
descriptive of actual usage, particularly in American English. None of my
dictionaries mention (much less sanction) this usage. I know it's a common
error, but I still insist that it's an error. Is usage winning this battle?

Paul
http://www.mcfedries.com/