Which term most closely matches the description: an expression of the risk associated with a hazard that combines its severity and probability into a single arabic numeral which can be used to determine hazard abatement priorities?

I would say a risk assessment rating would combine the severity and probability of a hazard occurring which if carefully thought out would allow an observer to know what amount of abatement would be necessary to alleviate the risk of the hazard creating physical damage say to production equipment or injuring someone.