St. Patrick's Day, Halloween, Mardi Gras. Those days that seem to, at least for college students, exist solely for the purpose of getting shit-faced drunk, with rituals often beginning as early as morning and continuing throughout the day.

someone who is sexy beyond mean

A holiday on which copious amounts of alcoholic beverages are consumed.

An occasion like Hallowe'en, April Fool's, or Father's/Mother's Day. Though not categorized as an official holiday, is often used as a good occasion to get a good drunk on with friends.

any random day of the week where everyone wants to drink all day but needs an excuse

A protracted happy party in which large quantities of alcohol are consumed. It can also be used while at a bar. Basically, if you're piss-drunk, you've had an alcoholiday.

An work day devoted to absenteeism and the drinking of alcohol. Typically a Monday.