A group of usually anything-goes dirtbag adverturers. Money is usually only a priority to only get somewhere or do something, otherwise, it's the trip that matters. Because they're usually young and dumb, they usually do pretty hazardous activities for fun like skiing or rock climbing or mountain biking, etc. A hazard assembly is a group of them.
A hazard assembly formed of about a dozen mountain bikers in the middle of fucking nowhere. I had no idea where they were actually going...