My own definition: If the ingredient list contains something that you are not exactly sure what it is, then it is processed.
Personally I consider a can of skipjack tuna in spring water to be unprocessed, even though it has been canned.
I consider a frozen bag of peeled and cooked shrimp to be unprocessed, even though it has been peeled, cooked, and frozen.
But a frozen bag of peeled garlic shrimp I would consider to be processed, because the ingredient list contains items I don't exactly know what they are.
So that's my definition, it's the ingredient list.
Personally I consider a can of skipjack tuna in spring water to be unprocessed, even though it has been canned.
I consider a frozen bag of peeled and cooked shrimp to be unprocessed, even though it has been peeled, cooked, and frozen.
But a frozen bag of peeled garlic shrimp I would consider to be processed, because the ingredient list contains items I don't exactly know what they are.
So that's my definition, it's the ingredient list.