No, I’m not going to point out that the primary definition of the word is, to quote the Oxford English Dictionary, “in a literal, exact, or actual sense; not figuratively, allegorically, etc.” There are plenty of people online reminding English speakers of that fact—most recently in response to a popular thread on Reddit and a post on BuzzFeed complaining about the fact that a secondary usage of literally can now be found in dictionaries. That BuzzFeed post is headlined, “The Wrong Definition of ‘Literally’ Is Literally Going In The Dictionary,” a headline that itself gets both language and dictionaries wrong.
How so? I recommend reading (or re-reading) Jesse Sheidlower’s Slate piece about literally, published back in 2005. Sheidlower, as it happens, is an editor at large of the Oxford English Dictionary. He points out people have used literally as an intensifier for statements that were not literally true since at least the late 18th century. And it wasn’t just anyone using the word this way: Jane Austen, Charles Dickens, Mark Twain—any number of respectable writers have thus employed literally. In The Adventures of Tom Sawyer, for instance, Mark Twain writes that Tom “was literally rolling in wealth.” But Tom is not, in fact, rolling around “in a literal, exact, or actual sense.”*
So was Twain using the word the “wrong” way? He may have been using it in a manner you consider inelegant or confusing. But are you really confused? Chances are you understand exactly what he means, just as you probably understand what someone means by a comment such as “my head literally exploded.” Literally for centuries, people have used literally as an intensifier, to emphasize the strength of their feelings about something. As Sheidlower notes, this is not unlike saying, to quote Meg in Little Women, “I’m really dying for some amusement.” Meg did not mean that she was dying “in reality; in a real manner,” or “in fact, actually,” as the OED defines the principal meaning of really.
The usage of really has expanded, just as the usage of literally is expanding. The meanings of words change over time. And dictionaries—the most respected standard ones, that is, like the OED—record how people use words. Basic dictionaries don’t primarily serve to provide guidelines for “correct” usage. When people despair that some neologism is going into some dictionary or another, they might as well be complaining that an entry about some animal they really don’t like is going to be printed in a zoological guide. These usages exist. Lexicographers keep track of them.
You’re free, of course, to argue that people shouldn’t use literally that way. I don’t think people should use disinterested (that is, as far as I’m concerned, “impartial, unbiased”) to mean uninterested (“unconcerned, indifferent”) even though I know that many people do, that they have for centuries, and that when they do so it’s not usually hard to know what they mean. It’s a matter of style and personal preference. And calling such usages “wrong” is an opinion, not a fact.
* Correction, March 6: This post originally used a passage from Little Women as an example of literally used as an intensifier. But that passage was using literally literally, as it were. It has been replaced by an example from The Adventures of Tom Sawyer.