Quite clear.
Very clear.
"Do I make myself clear?" / "Crystal."
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.