1) To have reached ones limit. Generally refers to the physical forced stopping point of alcohol consumption,and marijuana smoking that results from mass consumption.
2) Also synonymous with 'destroyed', 'wrecked', 'totaled.'
"No more tequilla man, im donescore"
"Oh @#$^ Johnny got hit by that car, he's donescore man."
"Johnny donescored himself tripping down the stairs drunk. Damn he looks like it hurt."