We need a word or phrase to refer to intentionally (and usually only slightly) misquoting something for the sake of a perceived æsthetic improvement in the context in which the quoter wants to use the material. Okay, we do have the word paraphrase, which is close ("To paraphrase the great fooer Bar Quux ..."), but I don't think that's quite it—the Wiktionary definition mentions "often to clarify meaning" and I'm definitely talking more about petty differences in word choice than actually clarifying meaning.
There's this wonderful quote by Eugene Gendlin that I often remember as "People can stand what is true, because they are already doing so," but it turns out that Gendlin's actual phrasing was "for they are already enduring it." If I want to use my slightly different choice of words because I think it flows better in the context in which I'm repeating it, I think that can be legitimate. (Although needless to say, in formal settings, you definitely only want quotation marks around the words someone actually said.)
Or if my hypothetical pop punk band (which would hypothetically be called either "Bullet Candy" or "Zack M. Davis and the Duty-Bound Empiricists") were to cover Taylor Swift's "The Story of Us", I would sing part of this one line in the chorus as "the twist of fate by which it all broke down" rather than the original "the twist of fate when [emphasis mine] it all broke down," not to suggest Swift was wrong to sing when, but rather because that kind of use of the phrase by which is exactly the sort of rhetorical flourish that my hypothetical band would hypothetically be known for.
We need different words for apology in the sense of "I'm sorry; I won't do it again," and apology in the sense of "I'm sorry that this lowers your utility, but not sorry enough to actually change the behavior in question; maybe we could negotiate some other behavior change that might partially make up for it." Both can be sincere, but they mean different things.
The other week I was reading a book that used the word multimegaline—from multi- and mega- and line, referring to software projects composed of many millions of lines of source code. But I prefer to believe that the last syllable rhymes with keen and that the word is good for anything really big.
You hear people accusing their enemies of being morally or intellectually bankrupt, and they mean it in the sense of "destitute of, or wholly lacking (something)", rather than the sense of financial insolvency. But I actually would like to see the insolvency metaphor: people should speak of declaring intellectual bankruptcy to mean "I was wrong before; I won't try to defend my previous claims because I can't" (in analogy to "I won't try to pay my debts, because I can't").
Loopy is slang for "crazy", but I think it should be repurposed to refer to the quality of thinking the same sorts of thoughts over and over again, never breaking patterns, being stuck indefinitely at the same stage of intellectual development. You could argue that this is a form of craziness compared how an ideal agent would allocate cognitive resources, but I think it's pretty normal and common in our world, not the kind of craziness generally recognized as crazy.
We need a word that means almost the same thing as sellout (in the sense of "a person who compromises their principles for financial gain"), but conveys the idea that the problem is not selling out, but selling out for too low of a price. We all have to make trade-offs; there isn't any one principle that takes lexical priority over every other valuable thing in life: sometimes it makes sense to compromise your ideals in exchange for money or power or fame or fitting in.
But you could at least haggle!
There are a lot of really important concepts that aren't easy to talk about, because we don't have standard words for them.
Like, there needs to be a word designating the skill or quality of possessing independent judgement—the ability to make decisions without getting distracted worrying about how to explain yourself to people who won't understand. Part of me wants to just call it sociopathy, but that's clearly not the right word.
The problem is endemic. Friend of the blog Mike Blume once lamented that we don't have a gender-neutral equivalent of gentlemanly. And we don't have an atheist equivalent of doing God's work, either.