What is considered a car accident (for car insurance purposes)?

When signing up for car insurance, it asks on the application whether the driver has been in a car accident in the past 5 years. What is considered a car accident? Let's say I hit someone, but both parties decided not to report it. As far as the insurance company is concerned, is that considered a car accident for their purposes or no?

In such a case, what would one answer? Yes or No?