In the state of Montana (perhaps elsewhere, I'm not sure) dirty 30 refers to a 30 pack of Keystone Light. Cheap shitty beer that all the hicks LOOVVEEE.
A young caucasian female who appears to be at the upper crust of society but instead is from a really ghetto area such as Springfield, Ma. which is full of stabbings murders and hoodrats.
Friend: I can't believe this is your last year in your 20's! You're getting old.
Me: Yeah, we should celebrate by having a Dirty 30 party. I need to get shit faced to deal with that!
Rasheed Wallace, number 30, forward for the Portland Trail Blazers NBA basketball team. In the world of sportswriting, Sheed is frequently criticized for his large salary, marijuana citation, large collection of technical fouls, suspensions, altercations and a racially charged Oregonian interview where he said the NBA exploits African-Americans.
The result of a dramatic increase in alcohol consumption combined with cafeteria style eating you encounter in First year of University. The Freshman 15 taken to a whole new level.
Trevor- have you seen Maddie lately?
Jordan- the weight gain?
Trevor- she's hit the dirty 30
Jordan- classic
Calum- getting a little husky there bud
John- I know, it's the dirty 30