To be under the influence of two substances. Marijuana and alcohol. With Marijuana you are Blazed or High, and with Alcohol you are drunk, or wasted. When you combined the two together you put both of then on top of another, or stacking them, hence forth you being, Stacked
"Dude, once i did that bong hit i got so stacked"
by Dieweak73 May 12, 2008