The biggest differences between alcoholism and alcohol abuse (alcoholic vs. drunk) are the following:
Alcoholism:
Narrowing of the drinking repetoire
Drink-seeking behavior
Tolerance
Withdrawal symptoms when intake is reduced or eliminated
Drinking to relieve or avoid withdrawal symptoms
Subjective awareness of a problem (whether admitted or not)
Inability to follow through on a commitment to quit drinking
At least this is what I gather from my research on the subject.
But does it really matter? If alcohol is getting in the way of your happiness, then eliminate it or reduce it. If you're an alcoholic, the only way is to eliminate it. Alcoholics (like me) are incapable of moderation.