An alcoholic is a man or a woman who suffers from alcoholism - they have a distinct physical desire to consume alcohol beyond their capacity to control it, regardless of all rules of common sense.
According to Alcoholics Anonymous UK, who say they have no unique definition for alcoholism, it may be described as a physical compulsion, together with a mental obsession. Apart from having an enormous craving for alcohol, an alcoholic often yields to that craving at the worst possible times. The alcoholic knows neither when nor how to stop drinking.