In a comical scene in the film The Princess Bride, the character Inigo Montoya has finally had enough of hearing the bad guy Vizzini say "Inconceivable!" when things are not only conceivable, but just keep happening. Montoya is finally moved to say, "You keep using that word. I do not think it means what you think it means."

Shannon Reed recently wrote a wonderful piece about how we often have mistaken ideas about how to pronounce a word we recognize on the page. It turns out that the same phenomenon occurs with the meanings of words, and I'll bet that most of us have had one or more moments in which we, too, learn that a word we've been blithely using as adults "does not mean what you think it means." There are words whose meaning we've picked up from context, or think we have, and we proceed to use without realizing just how incorrectly we understand them.

For example, when I was in my 20s, a colleague once confessed to me that he'd heard the phrase "erstwhile friend" as a youngster and deduced that erstwhile meant "esteemed" or "noble." He'd been using erstwhile with that assumption for years, and boy, was he mortified when someone finally clued him in that it actually means "former." (It's possible, though I might not have told him at the time, that I also had thought that until his confession.)

Similarly, I once worked for a little company that put out a monthly newsletter in which the CEO wrote a column. In one of his pieces, he talked up an "enervating new feature," apparently thinking that enervating meant "energizing." He was still living that one down years later.

One of the many Biblical parables concerns the prodigal son. In the story, the eponymous son gets his inheritance early, travels away, squanders his fortune, and then returns to his father when he's destitute. For years I thought that prodigal meant "went away and returned" or maybe "wandering." Actually, no: prodigal means "wasteful" or "lavish." 

I asked among my friends if they'd ever had this experience, and sure enough, everyone recognized the situation all too well. Someone said they'd grown up thinking that droll meant "dull." (Someone in the documentary Catfish also thought of it this way.) Another friend said someone he knew thought that overachiever meant a person who achieves more than they worked for. Yet another friend thought for a long time that avuncular meant "grouchy." A person I work with was mortified to discover that he'd been confused about abide — and that he'd discovered this years after he'd dedicated his Ph.D. thesis to his advisor for the professor's "unabiding support."

In each of these cases, when the person had derived a meaning from context — a droll person, an avuncular fellow — they'd drawn the wrong conclusion and had then gone years or decades before someone came along to correct their misperception.

Note that these aren't just examples of easily confused words like affect/effect or proscribe/prescribe. Nor are they examples of terms whose common usage is insufficiently precise for some people, like decimate and unique. No, these are terms where we've gotten a meaning in our head that's just flat-out wrong.

Sometimes this type of confusion becomes so prevalent that the "wrong" meaning has gained equal weight with the dictionary definition. A few years ago, Ben Zimmer wrote about the terms nonplussed and bemused, where "more people get it wrong than right." In that case, what's really right any more? It's possible that prodigal is heading that way; how many people use it these days in the sense of "went away and returned"? Plenty of people I've asked recently think that's exactly what it means.

An editor friend of mine went through a kind of crisis about all of this. His word is jejune; because he'd studied French, he assumed that the word meant "immature," related to the French word for "young," jeune. But jejune derives from a Latin word that means "meager" and has evolved via the sense of "thin, unsatisfying" to mean "dull" or "uninteresting." But jejune now actually is used to mean "immature." He'd discovered that he'd misunderstood the word for a long time, only to find out that the word had caught up with his misunderstanding.

Of course, the incorrect definitions I've gathered are only those where people eventually realized their error. When I asked friends for examples, one of them observed sagely that she probably has the definition wrong for quite a few words, only she doesn't know it yet.

I'm curious whether others have also had this "Aha!" moment when they realized, perhaps with a flush of embarrassment, that that word does not mean what they thought it meant. If so, leave us some examples in the comments (if you dare).