Jason posted a link to a book containing 100 words that the good people at the American Heritage Dictionary think you should know. Here are the 100 words. So... let's see how I do:

Words I know at least one of the definitions of: 81
Words I recognize but don't know the definition of: 5
Words I don't recognize at all: 14

I'm not sure if these numbers reflect well on my vocabulary or not. Jason suggests that the list is largely comprised of mostly worthless words, but I find his supercilious hubris a bit jejune, don't you?

Anyway, here are the words I recognize but couldn't come up with a definition for: antebellum, bellicose, circumlocution, unctuous, and winnow. I've definitely seen all of these words used, so perhaps I should look them up. [And now I have.]

Here are the words I have no memory of ever having seen, ever: abjure, abrogate, abstemious, bowdlerize, churlish, deleterious, expurgate, inculcate, jejune, loquacious, lugubrious, moiety, pecuniary, and quotidian. Obviously, I've already looked up jejune and used it, above... it seemed like the oddest of the list, to me. Having now looked up these words, I must agree with Jason on this list; most of these convey meaning that I basically never need to express. I seldom winnow.

Of the 19 words I didn't know the definition for, I find it interesting that they are mostly adjectives with common synonyms (11) or transitive verbs (6). The remaining two words are nouns. The first of these two nouns is moiety, and I'm willing to bet that you had to look it up too. The second noun is just a beautiful one—circumlocution:

n. The use of unnecessarily wordy and indirect language.

In a way I'm sort of glad I didn't know that one, as I find circumlocution really irritating. And I think the people who made this list probably engage in a bit too much of it.