A side-effect of cannabis use that causes the muscles of one's eyelids to become relaxed and slightly closed to take on the appearance of someone from Asian - or 'chink' - descent.
A similar side-effect sometimes called 'red-eye' can also occur if a user is a new smoker or just smokes a lot. This is caused from dilation of the capillary veins within the eyes.
Shit man, don't be chinking so hard when we get to school! The teacher's will know we're stoned!