I just got bmw and was trying to think of what it means!

the M tands for M-Sport, which in turn stands for Motorsport. The M series are the fastest of each particular model. The first M car was the Guigario design M1 supercar, which kind of flopped. It was made from 1979 by Baur.

Since then the M badge has been applied to each of the models after it's been tuned and tweaked.

M-sport is BMW's in house tuning wing. You will also find two more companies, Alpina and Hartge who have been long served recognized and approved tuners of BMW cars.

Motorsport. Loaded saloons which go like the wind.

"M" series is for Motorsports.