http://www.allaboutlifechallenges.org/alcohol-addiction.htm
Alcohol Addiction - What is alcoholism?
Alcohol addiction is simply defined as a compulsive need for an intoxicating liquid that is obtained from fermented grain or fruit. These liquids include beer, wine, and other hard liquors.
Alcoholism is present when a person craves alcohol and cannot limit or contain his or her drinking. If someone experiences withdrawal symptoms such as nausea, sweating, shakiness, or anxiety when alcohol consumption has ceased, or if there is a need to drink greater amounts of alcohol in order to feel a high, that person is most likely alcoholic.
http://en.wikipedia.org/wiki/Alcoholism#Medical_definitions
Medical definitions
The Journal of the American Medical Association defines alcoholism as "a primary, chronic disease characterized by impaired control over drinking, preoccupation with the drug alcohol, use of alcohol despite adverse consequences, and distortions in thinking."[2]
The DSM-IV (the standard for diagnosis in psychiatry and psychology) defines alcohol abuse as repeated use despite recurrent adverse consequences.[3] It further defines alcohol dependence as alcohol abuse combined with tolerance, withdrawal, and an uncontrollable drive to drink.[3] (See DSM diagnosis below.)
According to the APA Dictionary of Psychology, alcoholism is the popular term for alcohol dependence.[3] Note that there is debate whether dependence in this use is physical (characterised by withdrawal), psychological (based on reinforcement), or both.