really non-scientifically speaking, the kind of "processed" that seems to be less healthy comes closer to "pre-chewed/digested" and "concentrated" (ground very fine, broken down into constituent parts. Eg: refined flours over whole grains. corn syrup over corn on the cob (or even just frozen whole corn), Fruit juice over sliced fresh/frozen fruit.
A big challenge is how do you make rules/terms for that uneducated (on the topic) folks, disinterested folks, and lower IQ folks (MeanIQ - 1SD) can readily understand and apply in their busy + stressful lives?