Determining whether an action is considered cheating can be subjective and may depend on the boundaries and agreements within your relationship. While riding a motorcycle with another person of the opposite sex might not be inherently cheating, it could be seen as crossing a boundary if it violates the trust and communication expectations in your relationship.
The key issue here is transparency and communication. If your boyfriend didn't inform you about this activity, it might raise concerns about honesty and openness in the relationship. It's essential to have open conversations about what is acceptable behavior and what isn't to avoid misunderstandings and hurt feelings.
If you feel uncomfortable or hurt by your boyfriend's actions, it's important to communicate your feelings with him. Discuss your boundaries and expectations for trust and honesty in the relationship. Remember, healthy relationships are built on trust, respect, and open communication. It's crucial to address any issues that arise and work through them together.