"especially literary" would indicate that it can be found in writings, literature, or books classified as literature. These examples according to Youdao for caress "a gentle touch" or "kiss" that shows you love are less likely to be used outside of literature to express love. Hope that helps, Rob

It means that this word ("caress") is used, ad nauseam (far too often) in books.

In English and other languages, there are different levels of formality. "Formality" doesn't quite capture the idea. The technical word, I've learned, is "register." We write differently than we talk. And we write differently in different situations. "Literary" means that a word is normally used when writing, and normally only when writing in a "high register." You find it in books. You find it when someone is intentionally trying to "write well." Casual speech: "Holy cow! There it goes! Just _look_ at that thing! Wow! I'm glad we came! Whaddaya think, that's gotta be two hundred feet, do you think?" Blog post on a personal blog: "We visited 'Old Faithful' today. The eruption was really impressive. I'd seen pictures of it but I wasn't prepared for the real thing. It makes you wonder just what's really going on there underground!" "Literary" writing: "The celebrated 'Old Faithful' geyser emitted occasional puffs of mist. As the first splashes of water emerged, they wrung a collective sigh from the assembled multitude. Then the eruption proper commenced, a series of blasts reaching ever-increasing altitudes, until finally a steady jet shone as white as snow in the afternoon sunlight. I was minded of Coleridge's 'half-intermitted burst' and my awe was commingled with fear of the primal power, normally confined to the infernal regions below, but now so evidently revealed." In everyday life, I can easily imagine a member of a couple saying to the other, "Oh, come over here and kiss me, I need a kiss." I can't imagine anybody using the word "caress" in normal speech. If you were trying to teach someone how to milk a cow, for example, you would say "use a gentle touch, don't tug;" you would never say "caress the cow."