Just about everybody has taken to using the word "bubble" when talking about the housing market. Among the optimists who have embraced the idea is a condominium developer in Miami who is running an advertisement for two new properties that shows a woman blowing an enormous chewing-gum bubble above the word "Boom!" And at the Mortgage Bankers Association, the chief economist, Doug Duncan, says he subscribes to the Don Ho way of thinking, referring to the singer's hit, "Tiny Bubbles."

But the pessimists are not surrendering the metaphor they started. Robert Shiller, an economist whose book in 2000 predicted the stock market crash, has rereleased the book with a new cover warning of "the worldwide real estate bubble and its aftermath." All of which leads to the question: Does the word "bubble" have any meaning anymore?

In some cases, the word indicates a market in which prices have gone up so far and so fast that they are destined to crash, as some thought might have been happening when a recent report showed that apartment prices in Manhattan had dropped 13 percent from July through September. Others use "bubble" to suggest that prices could drift along for years to come. They might trail inflation for as much as a generation, even if the nature of real estate, with its slow and infrequent transactions, prevents a Nasdaq-like collapse.

To many developers, brokers and bankers, not to mention homeowners, who all have a big stake in the boom, the word has come to symbolize a fabulous market that is likely to slow eventually. The 15 percent annual price jumps of recent years will gently ease into 5 percent or 8 percent increases, they say.

Even some who insist there is no bubble in real estate use a similar metaphor. David Lereah, chief economist for the National Association of Realtors and the author of a recent book urging people to buy more real estate, said "air will come out of the balloon" in the coming months.

It is still not clear who will end up being right about house prices, but the vast housing industry has already chalked up one victory by muddying the linguistic waters like this. If the worriers convince you that there is indeed a bubble, but real estate agents tell you that it is not so bad, you might just go ahead and buy a vacation home with no money down.

Grant Barrett, a lexicographer for Oxford University Press in New York, likens this obfuscation to the linguistic tactics of politics.

"It's that weird behavior of trying to make a word mean what you want it to mean," Barrett said. "We call it the 'thesaurus defense.' It's basically redefining a word in order to suit their own point of view and in order to make themselves feel right or sound right."

To be fair, there is no precise economic definition of a bubble, and uncovering one in the housing market is particularly tricky. When the same question came up about the stock market in the late 1990s, the terms of the debate were clearer. People who used the word "bubble" generally meant that stock prices would soon fall sharply, which they did.

But the real estate market is not as volatile as the stock market. When house sellers cannot get the price they want, they often wait, instead of panicking. The worst declines in real estate values usually happen over years, often at the hands of inflation rather than in the form of a sudden decline. That means that even popped bubbles do not always go by that name.

During the most recent real estate downturn, in the late 1980s and early 1990s, prices fell more than 10 percent in New York and more than 20 percent in Los Angeles, according to the National Association of Realtors.

Adjusted for inflation, the losses were far worse: about 30 percent in parts of the northeastern United States and even more in Southern California. Prices peaked in about 1988 and did not return to their highs until about 2000.

"I don't believe real estate acts in any way that could be a bubble, because a bubble pops, and real estate doesn't explode overnight," said Pamela Liebman, chief executive of Corcoran Group, a large real estate firm in New York.

Just about everybody has taken to using the word "bubble" when talking about the housing market. Among the optimists who have embraced the idea is a condominium developer in Miami who is running an advertisement for two new properties that shows a woman blowing an enormous chewing-gum bubble above the word "Boom!" And at the Mortgage Bankers Association, the chief economist, Doug Duncan, says he subscribes to the Don Ho way of thinking, referring to the singer's hit, "Tiny Bubbles."

But the pessimists are not surrendering the metaphor they started. Robert Shiller, an economist whose book in 2000 predicted the stock market crash, has rereleased the book with a new cover warning of "the worldwide real estate bubble and its aftermath." All of which leads to the question: Does the word "bubble" have any meaning anymore?

In some cases, the word indicates a market in which prices have gone up so far and so fast that they are destined to crash, as some thought might have been happening when a recent report showed that apartment prices in Manhattan had dropped 13 percent from July through September. Others use "bubble" to suggest that prices could drift along for years to come. They might trail inflation for as much as a generation, even if the nature of real estate, with its slow and infrequent transactions, prevents a Nasdaq-like collapse.

To many developers, brokers and bankers, not to mention homeowners, who all have a big stake in the boom, the word has come to symbolize a fabulous market that is likely to slow eventually. The 15 percent annual price jumps of recent years will gently ease into 5 percent or 8 percent increases, they say.

Even some who insist there is no bubble in real estate use a similar metaphor. David Lereah, chief economist for the National Association of Realtors and the author of a recent book urging people to buy more real estate, said "air will come out of the balloon" in the coming months.

It is still not clear who will end up being right about house prices, but the vast housing industry has already chalked up one victory by muddying the linguistic waters like this. If the worriers convince you that there is indeed a bubble, but real estate agents tell you that it is not so bad, you might just go ahead and buy a vacation home with no money down.