Life is a 360 degree circle. You have 0 degrees (completely sober), 90 degrees (drunk), 180 degrees (high and drunk), and 270 (high). Getting "180'd" is the practice of smoking and drinking at the same time. Smoking and drinking at the same time tends to cancel out making you feel neither stoned or drunk. Some describe it as feeling "normal," while at the same time, they're completely fucked up. The reason we made it 180 degrees is because you go from 0 degrees to 180 degrees, and you may not even know it, because you're essentially crossing their circle into a new realm of being fucked up. If it doesn't make sense, that's probably because the entire concept was thought up while being 180'd. The best way to understand is to simply ... smoke up and put some shots down. Before you know it, you'll be 180'd.
Dude, you wanna get 180'd tonight?