PALO ALTO, Calif. (CNN/Money) - An important expression is creeping into conversations about the market these days: Bear-market rally. It describes a short-term spike that fools optimists into believing the downturn is over. If you're one of those cup-half-full types, pay attention.

When someone makes reference to a bear-market rally, they think you shouldn't get too excited about, say, the Dow's increase of 15 percent or so since its recent low on Oct. 9.

Take this typical prose from Alan Abelson of Barron's, writing in the current issue. "As last week's stock action ... revealed ... bear-market rallies do not go straight up. Incidentally, it's sure also to come as a shocking revelation to the revived herd of bulls that bear-market rallies don't last forever, either."

Two points there: Bear-market rallies aren't linear, and they don't last. In fact, they often don't last very long at all.

"A bear market is one whose dominant trend is down," says Mark Manson, director of research for Thomas Weisel Partners, the San Francisco investment bank. "A rally is when stocks are going up. A bear-market rally is a brief and sometimes violent period when stocks are going up in the context of the market going down."

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Now this all seems to be a lot of common sense, but it's easy enough to be fooled by a bear market rally. In retrospect, when stocks started running after July 23, it was just a bear-market rally, which we know now because stocks gave back all their gains by early October. But plenty of bulls had hoped that stocks would keep running then, and trotted out lots of "proof" that mid-summer marked a bottom.

Well, here we are again. If the Dow keeps moving up -- and stays up -- then you will be proven right if you've gotten in any time over the last few weeks. If the bear-market rally crowd is correct, however, your recent investments will simply enrich speculators whose timing proves better than yours.

My two cents? Consumers are scared, and the fact that the stock market managed to shake off -- for now -- yesterday's terrible consumer confidence report isn't going to help retailers trying to sell toys and clothes on credit this Christmas. Companies that are beating expectations have done so by re-setting the bar so low they can crawl over it. The tech washout isn't finished. And the bear market isn't over.

Adam Lashinsky is a senior writer for Fortune magazine. Send e-mail to Adam at lashinskysbottomline@yahoo.com.

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