"101.22 (a)(3) The term natural flavor or natural flavoring means the essential oil, oleoresin, essence or extractive, protein hydrolysate, distillate, or any product of roasting, heating or enzymolysis, which contains the flavoring constituents derived from a spice, fruit or fruit juice, vegetable or vegetable juice, edible yeast, herb, bark, bud, root, leaf or similar plant material, meat, seafood, poultry, eggs, dairy products, or fermentation products thereof, whose significant function in food is flavoring rather than nutritional."
--U.S. Food and Drug Administration Web Site, excerpt from Code of Federal Regulations, Title 21, Volume 2, Parts 100 to 169.
So what does this mean? Natural flavoring can be anything that comes from some plant or animal, and by looking at the hard links above, one can see that a flavorist can "process" the aformentioned plant or animal in any way needed to in order to get the desired effect. AND, there is no telling what is in the "natural flavoring" found in your ice cream...or your French Fries. This of course makes Vegetarians kinda unhappy, to find out that McDonald's uses "an animal source" in their fries. I read this first in an article by Eric Schlosser in the January 2001 Atlantic Monthly, and then noticed a ton of letters to the FDA on their web site asking for new laws asking for natural flavors to be expounded upon on food labels.
So the bottom line is: don't be fooled into thinking natural flavors are somehow better than artificial flavors. For example, in the same article, Mr. Schlosser shared his discovery that almond flavor can be derived from the "natural sources" of peach and apricot pits, or it can be created chemically. In either case, it is benzaldehyde, but in the natural case, it also will contain traces of hydrogen cyanide, since that is in the peach/apricot pits.
Oh, and I'm sure that this is not new news to those unfortunate enough to have severe allergies, but it may be new news to those of you with strict ethical or moral beliefs about particular foods: that little term "natural flavorings" (oh and not to mention "natural colors added") can mean that food you don't want to eat is hidden inside that can.
This is not a "rah rah" session for artificial flavors, either! Just realize that "natural flavors" are chemicals, also.