A fine type of glassware, or the material used to make it.
Crystal meth: methamphetamine hydrochloride.
A solid composed of an array of atoms or molecules possessing long-range order and arranged in a pattern which is periodic in three dimensions.
A piece of glimmering, shining mineral resembling ice or glass.
The glass over the dial of a watch case.
Very clear.
"Do I make myself clear?" / "Crystal."
Being, covered with, or pertaining to fog (“tall grass etc that grows after, or is left after, cutting; moss”)
Obscured by mist or fog; unclear; hazy
Confused, befuddled, etc.