[daveoc64]

There is a classification system for how processed foods are:

https://en.wikipedia.org/wiki/Nova_classification

Under that classification, boiling potatoes counts as processing them.

Something as minor as rinsing fruit in tap water can count as processing - it could affect the lifespan of the fruit or its nutritional content.

Of course, that isn't the only definition out there.

[haswell]

I think most people are referring to the “Ultra-processed” category when they talk about processed foods in a health context.