For me, this happens with the word “levity.” I totally understand what the word means, yet every time I hear it, I think of something heavy and ponderous and serious . . . exactly the opposite of its actual meaning. It takes me a few seconds to remind myself of the word’s actual meaning.
Interesting…I could have sworn that that usage was proscribed by the OED or somesuch, but now I feel less bad about all the times I used it to mean “skim.”
Thrive. Since I learnt the word from various nature documentaries that invariably used it in the sentence: Despite [various difficulties and predators] the [species] manages to thrive. I interpreted it as meaning manages to survive but only barely.
The OED exists only to describe language as it is used, not to comment on ‘correct’ or ‘wrong’ usages, and in fact has a little bit of information about this. Mods, I apologize if this quote is outside of the bounds of fair use.
In any case I’ve now found another one of my own. I could have sworn ‘proscribe’ meant to establish the use of something; of course I was confusing it with ‘prescribe’.
Cleave is what is sometimes called a contranym because it is its own antonym like with, sanction, clip, moot, oversight, dust and a number of other words.