When one attempts to draw the attention or initiate conversation with someone they know, only to be completely ignored, leaving the instigator looking like a total twat.
Today it usually means something like being ignored. During the Great Depression, the phrase was "eating air custard and wind pie"; that is, nothing to eat; going hungry.
When you are either a total noob at smoking weed or have such a chemical dependence and you dont have any glass so you just light it in your hand and breathe in the fumes.
Dude where is my piece, I need to smoke this weed.