Bolliger & Mabillard, roller coaster manufacturers. B&M coasters offer a very smooth ride, and the characteristic roar caused by the polyuthereane wheels on hollow track.
B&M is so called because of its founders, Walter Bolliger and Joseph Mabillard
Examples of B&M coasters include: Nemesis, Oblivion, Mantis, Raptor.
OMG that B&M was great! How do I know that was a B&M? By the characteristic roar! Did I mention I'm a rollercoaster enthusiast?