As much as speed-reading is in vogue, speed-learning unfamiliar words is still a rather less flaunted ability. Perhaps because it is harder to define.
Does learning a word mean acquainting yourself with its first meaning, with all its meanings, with its pronunciation, its origins, its examples and seeing its effect as you apply it in an appropriate setting? Learning has some degree of knowing as its goal. Can it be said that you know a word if, after having supposedly learned it, you have never again thought of it? (If your answer is yes, you haven’t ever attempted to learn a foreign language, and failed.)
Some words we get for free as we grow up; some we get for cheap by osmosis.
The setting often aids us: if I tell you of a milky-white small roundish object called X, and say it’s on a necklace, you might think it’s a type of pearl; if I say it’s on a plate, you might think it’s type of rice. But it could have been ivory in the first instance, and salt in the second. You can’t be sure, unless you’re sure of the word’s meaning.
Life is too short and language too multitudinous for us to know every word in every book we pick up. In fact, I am disappointed if I have failed to find a single interesting word in a text: unknown, referential, inventively used, made-up, altered—I am open to being surprised. Banal word-strings leave me with a sense of wasted time.
(In the strictest sense this can hardly occur, so I’ve set some minimum requirements for interesting words.)
In most cases, after having marked up my reading, I am left with numerous circled words which might merit investigation—and only a fraction of which will. That fraction is what I call the quirk words of a book.
Taken as a list, the quirk words can say a lot about a book: they cluster around the subject matter, they gravitate towards borrowings from the language in which the book was written (if not English), they’re dated to match the described era or the era in which the book was written.
This is not particularly surprising. A quirk list of a book varies from person to person, exhibiting the vocabulary deficiency of the reader with respect to that particular book. However, assuming we’re referring to fairly well-rounded readers, most of the words on each quirk list will be relatively rare in English overall (Frequency Bands 1–4 in the OED). These are the subject-related, the regional, the colloquial or the technical words—and each implies a specific application and context, narrowing down the kind of text it may be sensibly found in.
How about an example?