It is my understanding that this is a linguistic term, but I have coopted it to speak about data. Here, syntactic transparency and opacity is the ability, or not, to recognize a grammar in a data segment. Semantic transparency and opacity is the ability, or not, to understand what has been recognized. What I have below in fact describes syntactic opacity.

A data object - string, blob, file or stream is said to be semantically opaque if it is passed through a system without its contents being inspected or manipulated, as if it was a black box. Note, however, that unless empty or random, a given data segment would almost always have some sort of internal syntax and semantics.