Top executives call it getting "Uber-ized." Having "Uber syndrome." Or even the process of "Uber-ization."

Those are among the phrases that came up repeatedly in a new survey IBM conducted, which asked senior executives to describe their biggest fear. In other words, they are most scared of getting disrupted by a digital upstart from outside their industry, the way the ride-hailing company Uber has roiled the taxi industry.

The survey, which was released Tuesday, was conducted largely via face-to-face interviews by the IBM Institute for Business Value. It includes the views of a massive sample of top executives: More than 5,200 global C-suite managers such as chief executives, chief financial officers and chief marketing officers. Again and again, their fears of getting caught unprepared by these so-called "digital invaders" were among the top concerns they shared in the interviews and surveys.

"I can't begin to tell you how much [they talked about] disruption that comes from an unlikely competitor outside of our industry before we can see the competition coming," said Linda Ban, IBM's global C-suite study director. The study found 54 percent of C-suite executives expect to deal with that type of competition, a significant jump from the 43 percent who said so in 2013.

The angst over getting struck by their industry's equivalent to Uber is, of course, not exactly new. Ever since Clayton Christensen wrote "The Innovator's Dilemma," chief executives have been looking over their shoulder for unexpected disruptive technologies that might upend their company. But the frequency with which it's happening, and the way in which the upstarts are reshaping whole industries rather than just slowly pushing out veteran players, is what's keeping executives running scared.

"They've watched this happen - where another organization can come in and disrupted the business without having infrastructure, assets or armies of people," Ban said. "They're looking at that and saying, now where do I look for my Uber?"

The study also found that top executives of all stripes see "industry convergence" - such as the combining of sectors like health care and consumer electronics to form consumer-health gadgets like Fitbit - will be the biggest trend over the next three to five years, followed by an increasingly mobile workforce and growing cyber risks.

Two years ago, I.T. security was of little concern to executives regarding issues with new technologies; now, 68 percent of respondents say it's their top risk.