What does "M" stand for BMW?

This is M-town in BMW World, Munich. The flagship BMW brand store, “M” section. Lets take a look, what cars we have here:

BMW M5 Competition (1,930 kg)

BMW X3 M Competition (1970 kg)

BMW X4 M Coupe Competition (2045 kg)

BMW M4 Convertible Competition (1,846 kg)

So, what is the common nominator of these M cars. High price and about two ton weight. Too bad — not my kind of M. Weight for sure! M stand today for “luxury”, “high price” and “power”, but not for “agile” and “sporty”.