It's not meant to be a precise definition as most food is "processed" in some way. Rather it is a reaction against the excessive, unnecessary processing that

It's not meant to be a precise definition as most food is "processed" in some way. Rather it is a reaction against the excessive, unnecessary processing that is basically taken for granted, and everything that goes with it: pasteurization, hydrogenation of fats, ammoniated "beef," "meaty" foods†, GMO, high sodium content, high pesticide content, synthetic estrogens leaching from plastics, decreased nutritional content, rancidity, hormones, dyes, synthetic preservatives, etc., etc., etc. People who are more conscious of the hyperbole often prefer the term "minimally processed." † There are legal requirements for what percent of a meat needs to be present to be a considered meat, thus we get things like "beefy tacos" which contain a meat-like product with so much filler they do not meet the already low standards of what the USDA considers to be meat.