Disloyal (adjective)

1. Not loyal or faithful to a person, cause, duty, or country.
2. Betraying trust or confidence.

Origin:

From the old french word "desloyal" which means unfaithful.

Examples:

1. The disloyal employee leaked confidential information to a competitor.
2. The disloyal actions of the traitor caused harm to the country.
3. The disloyal behavior of the spouse resulted in the breakdown of the relationship.
4. The disloyal friends betrayed their promise and deserted him in his time of need.
5. The disloyal attitude towards the company caused the employee to lose his job.