The physical and mental state sometimes aquired by someone who consistently smokes, or used to smoke, a lot of weed. Typically characterized by the feeling and appearance of being stoned even when one is still technically sober.
See: Tommy Chong. The guy who works at your local smoke shop. Any stoner with a seemingly permanent smile and lazy eyes.
"Man, my dad hasn't smoked in years, but you can tell he's permastoned from his days on the commune".
refers to when a group of people are all getting high by passing around a pipe, typically made of blown glass, and the person currently holding it decides to start telling a story or a long-winded joke...completely forgetting that they're still in possession of the ganja.
Dude, enough with the glass microphone, pass that shit over here already!