first, I'm not sure whether it's possible to find a "scientific" meaning for "culture". Everything which is 'cultural' defies that kind of measurement and dry definition which is required for rigorous science. I think your question about the "external" meaning is just the very general thing that people outside academia sometimes use the same words as we do, but with quite different meaning. Notions like "culture", "society", "progress", "modernity" etc pp.
The difference with the use of such words in scholarly discourse is that the acdemics tries to think more thoroughly what they actually mean.
Regarding your "institutionalised culture", Bourdieu comes to my mind. I don't think that he uses the word "culture" a lot in his book "Distinction", but it is essentially about those modes of distinguishing oneself from others through "cultural capital". Habitus is the word. But those notions are, of course, not refering to "culture as it's meant in daily life". Besides, this notion of "high-culture vs low culture" to which you are refering (classical music, theater) is not the only way "ordinary" people use the word culture in their "daily" life. The "anthropological" sense of culture (as that thing which makes certain groups of people different, i.e. their language, customs, religion, rituals, etc), is also quite common for most people in our societies. Why are Chinese people so strange to us? It's not because of their biological characteristics - no, most of us liberals would say: it's kulcha.