All data, on some level, has "structure". Media files, blob data - there is all a measure of "structure" behind it. But as Brian alluded to - that structure in the case of a CSV is implied, because the data, as a CSV, is being presented in a raw form. Without getting too deep into semantics, delimited data is unstructured by definition, because, if you look at a CSV in notepad, for example, it's just characters - even if you account for the tabs/commas/etc that is used to provide "structure". Notepad doesn't look at the CSV data and see a "structure".
The only time data gains structure by definition is when that structure is applied by an external source. When we take that CSV and plug it into a framework, it gains some structure, making it semi-structured in this case. Though unstructured data has a native, internal structure that is based on the application that created it, there is no data model that organizes it in a predefined way; it is stored in its native format.
If that makes any difference in understanding...my humble 2¢.
/r