A person who owns more knives than years they have been alive, enjoys waving their fingers in the air while intoxicated, and is more proficient in knowledge and skill in any number of hillbilly weapons. This type of a person will quickly express his "abilities" for any activity if given the chance, and is better at anything than you are.
Me: Did you see that guy drive out of that police take down maneuver at 100mph!?!
Some Dirtsack: Aww that's easy, yah just shift it into neutral and get control of the wheel.
Me: You're a fucking dirtsack.
A nasty messed up person could be someone who drools, or is nasty in any way...it could be a guy who dates small framed girls that look two...it could be a small undeveloped girl that hunts for men...usually a messed up person that is quite spitefull and dirty to the max...:P
That katrina chick is a dirt sack shes dating a 40 year old.