I would say that a bevel is any angled cut, not necessarily used for joinery. A miter is a beveled edge (or set of beveled edges) cut to be joined.
I think you might find some people getting picky about it and saying that a "bevel" is along the length of the piece and a miter is on the width, but then what is it for a square?
If you go strictly by definitions (from m-w.com) ...
Bevel: "a slanted surface or edge on a piece of wood, glass, etc."
Miter: " a surface forming the beveled end or edge of a piece where a joint is made by cutting two pieces at an angle and fitting them together"
I'd say that supports my conclusion.
A miter is also a hat, but that's probably not so useful here.