The label “natural” on foods has never been officially defined, but it appeals to consumers nonetheless. Joe Raedle/Getty Images

The first two definitions of “natural” on Merriam-Webster’s online dictionary are “existing in nature and not made or caused by people” and “not having any extra substances or chemicals added.” When applied to food, however, the word often takes on a vague and in fact entirely different meaning. Customers are nevertheless undeterred, preferring to buy food labeled natural, even if they have no idea what that label actually means, according to a report published Wednesday by Consumer Reports.

In 2014, 59 percent of people regularly bought food labeled natural. In 2015, that proportion rose to 62 percent, the report found. At least 60 percent of people believed that the label “natural” meant a food had no genetically modified organisms, or GMOs, as ingredients, no artificial ingredients, no artificial colors and no chemicals.

They don’t exactly have the right idea, because “natural” has not yet been officially defined for food sold in the U.S.

“From a food science perspective, it is difficult to define a food product that is ‘natural’ because the food has probably been processed and is no longer the product of the earth,” the Food and Drug Administration says on its website. The agency has no official definition for the term natural, it added, and it doesn’t object to its use “if the food does not contain added color, artificial flavors, or synthetic substances.”

Recent debate over what constitutes “natural” and how it is defined has been vociferous enough that the FDA put out a request for comments on the use of the term in food labeling. The comment period, which closes May 10, asks the public to offer thoughts on the appropriateness of defining the term and if so, how it should be defined and how the term should be used to label food. The FDA put forth the request in part after receiving three citizen petitions that asked the agency to define or to ban the word on food. Common sources of debate include whether genetically engineered ingredients and sweeteners like high-fructose corn syrup count as natural.

The FDA acknowledged in its request for comment that its existing policy on the use of the world natural did not take into account the way food is grown and produced. If pesticides are sprayed on a fruit or vegetable, for instance, can it be considered natural? Other processes, like pasteurization and irradiation, went similarly unaddressed.

But for customers, the label “natural” is still appealing. In fact, 87 percent of those surveyed by Consumer Reports said they’d be willing to pay more for “natural” food, if it met their expectations.

“If there’s a health claim on the front of the package, that’s what we zero in on,” David Just, a professor of behavioral economics at Cornell University, told USA Today. “They’re interpreting those as, ‘This is going to have some different impact on the way my body functions after I eat it.’ ­”

All of this boils down to the fact that the term natural is confusing, or perhaps even misleading. The findings from Consumer Reports noted that at least seven products that had “natural” labels also had artificial preservatives.

Food companies do this because they can get away with it, and because they know customers are more likely to buy foods labeled natural, Urvashi Rangan, director of food safety for Consumer Reports, said.

“They’re trying to capitalize on a market where they know consumers want these things,” he said.