The definition of prejudicial is something that causes harm or damage, or is detrimental.
When a person is on trial for a crime, information indicating that he has previously committed similar crimes is an example of prejudicial information.
causing prejudice, or harm; injurious; detrimental
- Causing or tending to cause harm, especially to a legal case: a prejudicial error.
- Showing or full of prejudice; biased: a prejudicial opinion.