When you accidentally pass a single, small, bean-shaped portion of feces; whether in trust of flatulence, or, when momentarily failing retention of highly pressurized feces. Usually a precursor to deluge or projectile diarrhea.
“So, anyway, I was putting her in the Master Blaster, then…oh….oh, no….BOSS! I gotta go home! I slipped a bean. Yes, again!”
A Montreal Brown Bean Syrup is the action of shitting on a cock and smearing it and then getting your cock done the same. You then proceed to connect both tips at a 45 degrees angle so that each others dick are pointing straight at each others faces. After that you jerk the other person and time it exactly as to bust at the same time. The goal is to look like two brown beans (the cocks) are shooting syrup (cum) at themselves.
YOU: Hey mom! Arthur and I did a Montreal Brown Bean Syrup on your bed yesterday and i'd change the bedsheet if i were you since we got a little bit messy!