ICAO Doc 9735, Safety Oversight Manual” has this definition:
A condition in which the risk of harm and damage is limited to an acceptable level.
The Air Navigation Commission (ANC) has adopted the following definition of Aviation Safety:
The state of freedom from unacceptable risk of injury to persons or damage to aircraft and property.
Another way of saying basically the same is to say that acceptable SAFETY means that all risk levels are kept below the risk limits, ALARP, or that all hazard scenarios are kept in the acceptable region of the Tolerability matrix.