Idiom Savant is the latest example of that put-upon, widely ridiculed genre, the slang dictionary. These medium-sized, trivia-packed monsters are a perennial white elephant in the nonfiction department of any bookstore, and when encountering one of them, it is your duty as a reader to perform a sort of hipness-accuracy litmus test: Turn immediately to a section of slang which "everyone" knows and see how the authors handle themselves. Music slang terms, for instance, are good touchpoints, and Smithsonian writer Jerry Dunn stumbles right out of the blocks—it seems that "axe" is a term rock 'n' roll musicians assign to their guitars, and that "baby" is an affectionate term of address to males and females alike. Turning to the drug slang section, we learn that "baked" means very stoned, and that a "bong" is a pipe with a water chamber. When one looks up "weed" and reads the list of 22 other terms for pot, the droning voice of Jack Webb can be heard ticking them off inside your head. It's funny for all the wrong reasons, and it makes you mistrust the book. Dunn's definitions are correct, at least in these examples, but the very fact that he included such transparent and common terms shakes the reader's confidence in the sections on prison slang, for instance, or FBI-agent slang. If the easy stuff is that hard for him, does he really have a handle on the secret language of hardened convicts and government men? Will this book, mildly entertaining though it is, seem ridiculous in five years? Probably. It's a living language we've got, and you can find the colloquial definition of "baby" in a modern standard dictionary. "Bong," too. Idiom Savant, like many before it, is a good idea, but it's not a key to any secret hidden worlds of language.