A person who constantly gets in trouble by
breaking the law, lying, cheating or slacking off and expects everyone around them to take the blame for those offenses. A rat usually gets away with it by accusing others of offenses to push blame off of themselves (these are usually lies).
A rat will also take credit for anything positive, such as the hard work and accomplishments of others and when they get caught they are the first to call others a rat in order to place blame on others.
A rat never takes the blame for his/her actions, and they will fight tooth and nail to prove their innocence and escape justice.
A rat pollutes the
neighborhood, workplace or any other
environment, making it unlivable for others.