1. Concerning how a person acts in a faithful manner and can be trusted and depended on: Jim has always known Judy to be reliably optimistic because she inevitably has something positive to say of any situation that arrises, even though it might be a disastrous one!
2. Referring to something or someone that can be trusted or believed because of working or behaving well in the way one would expect: The dishwasher was always reliably efficient and never broke down.