This semester I assigned my museum studies students some readings from ICOM's Key Concepts of Museology (PDF). It's a theory-heavy document, as you might expect from a committee made entirely of French speakers (we read the official English translation). But I loved some of the ideas we discovered in it.
Here's one: A museum is "organised in order to enter into a sensory relationship with objects." What do you think: does that cover it?
It's awfully simple, yet it elegantly includes both research activities and public involvement. The writers acknowledge that museums have mostly engaged our sense of vision, but this definition leaves open other possibilities, and we've been learning how effective multi-sensory exhibitions can be.
In class, we also discussed the notion from Key Concepts that museums "establish a viewpoint on reality," They attempt to represent reality using objects that have been separated from reality in order to become symbols of it. Theory-heavy, right? I won't go on about it, never mind try to explain "musealisation," but I could...