alt Hacker NewsLike most of all widely spoken languages, there's a lot of regional variation in English. There's even a bunch of quizzes online where you answer 20 questions about phrasings, and they can tell you where you're from with a disconcertingly high degree of accuracy.
In my experience a "retort" is sharp or witty, but certainly not angry, whereas the word "rebuttal" is itself essentially antagonistic. You might use it when referring to something or someone that you look down upon, whereas a more neutral term would simply be "response."
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Just as I was reading your comment I remembered that Samuel Jackson used "retort" in his speech in the "Pulp Fiction" movie and was wondering whether he was openly antagonistic there (I mean, he killed a bunch of guys with a pistol shortly afterwards but still) or was it a witticism.
I admit I am lost on these nuances and I usually kind of use whatever idiom comes to mind, which yes, likely would net me some weird looks depending on where I am geographically.
Just personally I tend to regard retort as short and reactive while rebuttal as a longer and more considered disagreement. A retort could be defensive and wrong or it could be sharp and insightful - it doesn't imply one or the other. A rebuttal is mostly an attempt to correct something while a retort doesn't need to be a correction (although it could).
Even something like "piss off!" could be a retort, but usually never a rebuttal :)