A more thorough explanation:

Definition: not exposed to danger; not causing danger. Unlikely to be overturned or proved wrong.

• Wearing a seatbelt while driving is a safe practice.
• Staying away from dangerous neighborhoods is a safe decision.
• Investing in a diverse portfolio is a safe financial strategy.

The examples illustrate the first part of the definition, which means that something is not exposed to danger or does not cause danger. Wearing a seatbelt while driving reduces the risk of injury in case of an accident. Staying away from dangerous neighborhoods reduces the risk of being a victim of crime. Investing in a diverse portfolio reduces the risk of losing all your money in case one investment fails.

The second part of the definition means that something is unlikely to be overturned or proved wrong. For example, a scientific theory that has been tested and proven over time is considered safe because it is unlikely to be disproven. Similarly, a decision based on solid evidence and careful consideration is considered safe because it is unlikely to be proven wrong.