1. Ferocious and violent; carried out with intense violence and an apparent desire to inflict serious harm, or acting in an aggressive, cruel, and violent way: Roy's cousin had a vicious temper and would attempt to yell at anyone who taunted or bothered him.
2. Dangerous and aggressive and liable to attack or bite: Dina's vicious dog was kept on a strong leash whenever he was taken out for a walk.
3. Conveying maliciousness and intended to cause someone mental anguish or to defame that person: Gossips often have very vicious tongues and take pleasure in causing discomfort among their victims.
4. Pertaining to extremely severe or powerful and damaging results: The effect of the vicious hurricane was reported widely in the press which used graphic photographs.
5. Involving a chain of cause and effect or action and reaction in which things get progressively worse: After her fall on the concrete steps, Allison felt as if she were caught in a vicious cycle of appointments; first the doctor; followed by the therapist, then the home nurse, etc.
6. Wicked and immoral; such as, displaying or given to immoral behavior: Hanging out with street gangs was a vicious behavior that often got Lawrence into trouble.
7. Etymology: from Anglo-French vicious, Old French vicieus, from Latin vitiosus, "faulty, defective, corrupt" from Latin vitium, "fault".