crystalline : Idioms & Phrases

• in the Ptolemaic system of astronomy, two transparent spheres imagined to exist between the region of the fixed stars and the primum mobile (or outer circle of the heavens, which by its motion was supposed to carry round all those within it), in order to explain certain movements of the heavently bodies.

Webster 1913

• noun biconvex transparent body situated behind the iris in the eye; its role (along with the cornea) is to focuses light on the retina
  lens; lens of the eye.
  

WordNet

• (Anat.), the capsular lenslike body in the eye, serving to focus the rays of light. It consists of rodlike cells derived from the external embryonic epithelium.

Webster 1913