A person who is dependent on alcohol physicially or mentally. They can be anyone you know. Some hide their drinking from everyone, but others might show their lack of restraint in drinking in public. They also suffer sever liver, brain and esophageal damage from the accumulated years of drinking and abusing drugs.
Many of these alcoholic people also abuse their spouses, children physicially, emotionally and/or sexually, especially when they are drunk.
Our alcoholic father was so drunk he was fucking our little sister and he didn't even remember doing it the morning after.