meth, methamphetamine, or more specifically, crystal meth. a very "pure" form of meth, pure not meaning clean or safe, crystal meth is the farthest thing from clean and safe. Crystal is meth that can be smoked, is extremely dangerous and addictive, and is guaranteed to fuck up your life irreparably.
Stoner: "Hey man I just scored some awesome crystal, wanna buy a gram?"
Not Stoner: "Hell no! Pot is one thing..crystal is another."