That same 7,015-person study also found that sizable majorities reported owning a home, receiving a "good education," finding a "decent job" and giving their children better lives than they themselves had—all traditional tenets of the American Dream. Although these findings may not seem intuitive, the answer behind this discrepancy could lie in an important trend in American financial security.

The poll, conducted by marketing firm DDB as part of its 2014 Life Style Study, found that only 40 percent of American adults over the age of 18 believed they were "living the American Dream."

A new study shows that a majority of Americans are living the American Dream—even if they largely don't realize it.

Two sisters play on a tire swing in front of their house in Idaho.

"Even though people report that they are not living the dream, they actually are when you look at the traditional benchmarks," said Denise Delahorne, SVP, Group Strategy Director, DDB Chicago, who worked closely with the survey. She theorized that many people do not see themselves as having attained the traditional American Dream because of a shifting definition of the term.

"If you're new to this country, then life seems pretty good here," Delahorne said. "But for many people who have lived here a long time, they've started to think of the American Dream less as the traditional elements, and more relative to wealth."

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In the DDB survey, only 25 percent of adults reported that they have been able to "make a lot of money" in their life.

But Erin Currier, director of economic mobility at The Pew Charitable Trusts, told CNBC she does not think the disparity between the DDB respondents' life histories and their own assessment of American Dream fulfillment lies in an evolving definition. Still, she agreed with Delahorne: The explanation lies in wealth.

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"[American families] have enough that they are able to consume those indicators of the American Dream, but they aren't financially secure," Currier said, drawing the distinction to an increase in citizens' incomes, but not their wealth. "My instinct is that people feel that on a day to day basis."

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Because Americans are "treading water," she said, they are too insecure to be able to enjoy their achievements. Still, Pew research from 2009 confirms that the elements listed on the DDB survey roughly align with what citizens see as the American Dream.

The margin of error for DDB's poll is +/- 1.2 percent.