A more thorough explanation:

Definition: A prophylactic is something that is designed to prevent a particular disease or condition from occurring.

Examples:

• Wearing a condom during sexual intercourse is a prophylactic measure to prevent the spread of sexually transmitted infections.
• Taking a daily dose of aspirin can be a prophylactic measure to prevent heart attacks.
• Getting vaccinated against the flu is a prophylactic measure to prevent getting sick during flu season.

The examples illustrate how a prophylactic can be used to prevent different types of diseases or conditions. In each case, the prophylactic measure is taken before the disease or condition occurs in order to prevent it from happening.