WASHINGTON — What is it, exactly, that white people mean when they call a black person "articulate"?

I'll leave it to Joe Biden to explain (or figure out) why he used "clean" as one of a logorrheic string of adjectives describing his Senate colleague Barack Obama. I'm not sure his initial revision and extension of his remarks — that he meant "clean as a whistle" — get him off the hook. Just a suggestion, but Biden might fall back to "clean as the Board of Health," meaning sharply dressed; the last time I saw Obama he was, indeed, wearing an impeccable navy-blue suit.

For anyone who missed it, Biden explained Obama's appeal as a presidential candidate by calling him "the first mainstream African-American who is articulate and bright and clean and a nice-looking guy." He was talking to a reporter for the New York Observer, who recorded the interview; an audio clip was soon posted on the Internet.

There was a sharp reaction, mostly focused on Biden's incomprehensible reference to personal hygiene. The Rev. Al Sharpton, a one-time presidential candidate, said that when Biden called him to apologize, "I told him I take a bath every day."

For my part, I never made it past "articulate," a word that's like fingernails on a blackboard to my ear. As it happens, President Bush used that same word Wednesday to describe Obama. "He's an attractive guy. He's articulate," Bush told Fox News.

Will wonders never cease? Here we have a man who graduated from Columbia University, who was president of the Harvard Law Review, who serves in the U.S. Senate and is the author of two best-selling books, who's a leading contender for the Democratic presidential nomination, and what do you know, he turns out to be articulate. Stop the presses.

It's interesting that Obama's reaction dealt solely with the A-word. "I didn't take Senator Biden's comments personally, but obviously they were historically inaccurate," he said in a statement. "African-Ameri- can presidential candidates like Jesse Jackson, Shirley Chisholm, Carol Moseley Braun and Al Sharpton gave a voice to many important issues through their campaigns, and no one would call them inarticulate."

Maybe he heard the screech on the blackboard, too.

Yes, I'm ranting a bit. But before you accuse me of being hypersensitive, try to think of the last time you heard a white public figure described as articulate. Acclaimed white orators such as Bill Clinton and John Edwards are more often described as eloquent than articulate.

What's intriguing is that Jackson and Sharpton are praised as eloquent, too — both men are captivating speakers who calibrate their words with great precision. But neither is often described as, quote, articulate. Apparently, something disqualifies them.