Contronyms, also called antagonyms, auto-antonyms, Janus words, or enantiodromes, are those funny words whose multiple meanings are opposites of each other. There are
various reasons why such words have come about, including different words converging, as well as one word developing in two directions. For the most part, speakers of English can tell which meaning is intended without difficulty from context, for example:
Dust, seed, and stone can all be used as verbs meaning either to take their noun away, or to put it on, in, or at. Dust the bureau or dust the crops, seed the cucumbers or seed the garden, stone the peach or stone the sinners…
There are several words where the opposite meanings are marked by slightly different grammar, such as different prepositions:
You can cleave to your spouse and live happily ever after, but if you cleave your spouse, things must be very unhappy. In this case, the two meanings of cleave, “stick together” and “cut apart”, come from completely different Old English roots whose pronunciation eventually converged. Luckily, the preposition to prevents ministers using the Book of Common Prayer from urging murder on newlyweds.
Things really get fun when you find situations that leave the meaning potentially ambiguous.
What stays most unbudging, the faster it is? Dye, of course. In this case, fast originally meant “unmoving, steadfast” in Old English. It developed its sense of “quickly, swiftly” by way of “strong, vigorous.” Compare run fast with run hard, for example. Also think of fast asleep. (By the way, fasting as in “not eating” is from the same root, from the sense of being steadfast in observance of a religious duty.)
Consider “The alarm clock went off.” Was there a power outage, or is it time to wake up?
Why is that in baseball you don’t want to strike (miss), when the whole point is, after all, to strike (hit) the ball? Originally baseball players did mean hitting the ball with the word strike, having either fair or foul strikes of the ball. Apparently around the turn of the last century “foul strike” was shortened to “strike,” which then retained only its negative meaning.
Did the supervisor’s oversight mean things were closely inspected, or carelessly unregarded? “Supervision” came first, and “omission” about 150 years later. Interestingly, this word is ambiguous only in the noun form. In verbs, the attentive supervisor oversees, and the careless one overlooks.
You may look around as your party’s winding down and ask who’s left… But will the answer include those who are still there or those who have already gone? The ambiguity here works only because of the coincidence that in English both is and has can be contracted to ’s. The actual words clearly mark who is left as staying and who has left as going, because the first is the passive voice and the second is active. The same principle would work if you looked around at the end of the cannibals' feast and asked who’s eaten. The only difference is that the frequency of the passive construction to be left has led to left taking on the usage and properties of an adjective meaning remaining as well as being the past tense of the verb leaving.
If someone is livid, is their face greyish blue (like a bruise), is it white, or is it red? The dictionary includes all three different color definitions, even though they seem quite opposite. (Can you have a triad of opposites?) The first is the oldest and probably most correct usage. (It’s also the one referred to when detectives talk about lividity.) But on a light-skinned human, a greyish-blue complexion can also be interpreted as pale, leading to the second meaning. The third derives from the idea of a face being flushed dark, but probably comes from misunderstanding the original idea (as well as the Latin root, which means “bluish, black and blue.”)
While researching for this post I found several lists of alleged contronyms, but I didn’t consider most of them to be truly in this category. There are lots of words that can be used in opposite contexts, but with the word itself keeping the same essential meaning.
For example, if you cut in line you’re joining the line, but if you cut a class you abandon it. Is cut a contronym? I don’t think so, because the word cut still means “slice” either way. It’s only a question of whether you’re slicing a line in half in order to slip into the gap or slicing a class right out of your schedule.
Or if you toss out several ideas, are you adding them to the brainstorming pool, or eliminating them from it? It doesn’t matter, because toss means “throw” either way. Just because you can toss something either in or out doesn’t mean toss is its own opposite.
I’m also not counting slang meanings where bad means “good”, for example, since those are deliberately self-conscious about being their opposite.
As a bonus, here's a word whose two meanings aren’t strictly opposite, but unlike most of the contronyms it’s actually prone to misunderstanding in the real world:
What do you do if the teacher tells you you have outstanding homework? (Does it make a difference to say that your homework is outstanding?) Will your grade be an A+ or a zero?
Contronyms are just one of those fun quirks of language that make life potentially confusing, but more likely amusing. As for the word itself, it was coined in 1962 by Jack Herring.
[Pictures: Janus figures, copper engraving from Le imagini dei degli antichi by Vincenzo Cartari, 1608 (Image from Internet Archive);
Images of Janus, from L’antiquité expliquée et représentée enfigures by Bernard de Montfaucon, early 18th century (Image from Wikimedia Commons);
Janus, woodcut by Bolognino Zaltieri from Imagini dei degli Antichi by Cartari, 1571 (Image from Giornale Nuovo).