What is the difference between a moderate and a social drinker?

Moderate drinking is one drink a day for ladies, two for men. (Women are more susceptible to the effects of alcohol.) "One drink" means one 12-oz. beer, one 6 oz. glass of wine, or one 1.5 ounce shot of liquor, whether or not in a mixed drink.

We don't know what social drinking means, but it is often used as a cover-up for drinking that is -- how do I say eet? -- other than moderate.