What's a word you've spent a long time not using right?
Just recently I was in a conversation with a number of UK mainlanders and we had a debate over what "tories" meant, apparently disproportionately ordinarily it refers to a political party and it's not usual to use it as short for "territories" as I've used it (according to how the debate ended, it was half and half between them). And once again I'm reminded of how people feel to look back at their usage of a word/phrase over the years and cringe.
More tragically, me and a friend were embarrassed once upon realizing everyone was confusing "encephalitis" with "hydrocephalus" when talking to someone about their kid with hydrocephalus. Awkward because encephalitis is caused by HIV.
Since OP is in the UK, I can pull out “nonplussed.” Current American usage of the word is a lack of surprise or general acceptance. I am nonplussed when news arrives that another politician was caught in a sex scandal. Non-American usage is complete surprise and an inability to act. The Scot was nonplussed when the drunk American vomited noisily on his shoes.
Edit: I am firmly in the “general acceptance” camp and usually have to process for a second or two when someone uses it in its traditional sense.
Likewise, only ever known it as the total surprise meaning.
I wonder if the American meaning has any relation to the seemingly common use of the phrase "I could care less", which is similarly opposite to its (to me) correct meaning.
Oh and don't get me started on uninterested/disinterested...
It’s also generational. My dad was very confused (dare I say nonplussed?) when I used the informal meaning. IIRC he corrected me which is what led me to realize the difference. It seems to go back to at least 2013.
Words like those are common enough, and there's normally no problem in understanding them. When's the last time you misunderstood the word clip or dust?
That's cool! I've never heard of a contronym before.
However the difference is that most of those have different usages - e.g. if you say "I'm going to clip the hedges" vs "I'm going to clip something to the hedges", you have to use the word differently. With "dust", it's different based on the context, because you need to be talking about some sort of powder to be talking about putting something on. If I said "I'm going to dust the furniture", you would assume I meant clean, but if I said "dust the furniture with cleaning powder", you'd probably understand the difference. Different locations and activities also help here (e.g. skiing, cake decorating, cleaning, etc).
Nonplussed on the other hand likely derives its alternate meaning from an incorrect understanding of the original meaning, and so it's used in the exact same manner and context to mean the exact inverse. If I say the sentence "he was nonplussed at the news", which meaning am I referring to?
"Table" is another contronym that's ACTUALLY confusing (learned that one from this post as well).
Not in the UK itself (hence I distinguish them with "mainlanders"), just someone who has lived a commonwealth/territorial upbringing and has moved around a few times. The debate with said mainlanders sticks out because people within the physical UK differ largely in how they say things, and when you emulate them and fail from the perspective of someone from a lesser part of the anglosphere, you can't make the case as well that it's just a matter of different equally valid uses for the same vocabulary.