Not all that long ago, the phrase "double-dip" meant a delicious, icy dessert. But alas, all too often today that same phrase is followed by the ugly word "recession."

Though the National Bureau of Economic Research -- the folks that call the official beginning and end of economic cycles -- has yet to declare the recession ended, the U.S. economy has definitely shifted trajectory since its 2007-to-2009 plunge. Even if we set economic indicators aside, the stock market has definitely registered its vote in favor of a recovering economy.

But like Die Hard's John McClane, the global economy just can't seem to avoid trouble. And nasty trouble at that. As a result, many market-watchers continue to see the potential for the U.S. to slip back into recession in the coming quarters.

Yeah, right on!
Plenty of data points paint a none-too-flattering picture of the tenacity of the economic recovery. Front and center on everyone's mind right now is the unfolding situation in Europe.

Greece has been grabbing all of the attention when it comes to profligate EU countries weighed down by enormous debt loads, but all of the PIIGS (Portugal, Italy, Ireland, Greece, and Spain) have the potential to cause problems for the eurozone. As the EU is a major U.S. trading partner, austerity-induced economic slowdowns in those countries would impact the U.S. Likewise, declines in the value of the euro make U.S. goods less price competitive not only in Europe, but around the world.

Of course, we don't have to rely on Europe for economic difficulties; we have plenty of homegrown troubles. Big banks like Citigroup (NYSE: C) and Bank of America (NYSE: BAC) appear to be moving in the right direction, but they're also still being fed ridiculously cheap capital thanks to the rock-bottom federal funds interest rate. It also seems questionable at best whether the U.S. housing market is really on the mend. Indicators have shown movement in the right direction, but the market has also been significantly goosed by handouts from Uncle Sam.

And while it may not be useful to try and compare the U.S. economy to that of Greece, it's tough to ignore the fact that the cancer in that country's economy -- a hefty debt load and big budget deficits -- can also be found right here in the U.S. of A.

Heck, even some good news may not be what it seems. Last Friday, retail sales growth of 0.4% should have been good news. However, as my fellow Fool Seth Jayson pointed out on the Motley Fool Money radio show, much of the gains came from spending on home and garden items from places like Home Depot (NYSE: HD) and Lowe’s (NYSE: LOW). Seth's view is that those gains are a reflection of the funny money that the government was pumping into the housing market, not a broader pickup in retail spending.

The only thing we have to fear ...
Interestingly, Yale economist and financial-bubble watcher Robert Shiller penned an op-ed in The New York Times earlier this week suggesting that the thing we should fear most when it comes to a double-dip recession is ... fear of a double-dip recession.

To be sure, many economic indicators do appear to be moving in the right direction. Manufacturing has been making major gains, public company earnings have been trouncing expectations, and even the housing market has been surprising people to the upside. But in the end, confidence and sentiment still hold the keys to the kingdom when it comes to crucial economic drivers like lending, spending, and hiring.

And as Shiller pointed out, there has been an assault on sentiment in the U.S. lately. Take the May 6 "flash crash" for instance. With a stalwart like Procter & Gamble (NYSE: PG) falling as much as 36% and Accenture (NYSE: ACN) ludicrously trading down to $0.01, it's pretty obvious that what happened was a market malfunction. But that doesn't seem to matter. The event has gotten into the heads of investors and has many folks starting to talk about a potential repeat of the 1987 crash.

Though the situation in Europe definitely poses a tangible economic threat to the U.S., Shiller suggests that the images of people rioting in Athens may have an even larger psychological impact. And from there we could add in any number of events tangentially related to the economy, but potentially psychologically troublesome: the oil leak in the Gulf of Mexico, the unrest in Thailand, or the government investigations of Goldman Sachs (NYSE: GS) and other financial giants.

How likely?
Shiller was quick to point out that a double-dip recession still seems unlikely, noting that "when inflation-adjusted G.D.P. has come out of a decline and posted three or four quarters of gains, it has never immediately begun to fall again -- at least not since quarterly numbers began to be issued in 1947."

But a lot rides on which definition of a double-dip recession you subscribe to. For Shiller, it's any time the economy goes back into recession before employment has returned to a normal level after the previous recession, which is exactly what happened in the recessions of 1929-1933 and 1937-1938. Under that definition, it can be years between recessions and still be considered a double dip.

Whether we're in for that this time around will depend a lot on whether we can shake that creeping sense that something is about to go very wrong.

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