A state of being in which one is extremely drunk. Possibly to the extent where beginning to justify one's actions is nearly impossible.
The act of intoxicating oneself to an "above average" level.
Sally: "I can't BELIEVE the things you were doing at that party last night!"
Dave: "Why? What did I do? All I know is that I was shamamahammered last night... so I can only imagine what I did."
As a verb:
"Let's get shamamahammered tonight!"