Source : Webster's Revised Unabridged Dictionary (1913)

Diaglyph \Di"a*glyph\, n. [Gr. ? to engrave; dia` through + ? to
   carve.]
   An intaglio. --Mollett.

Source : WordNet®

diaglyph
     n : glyptic art consisting of a sunken or depressed engraving or
         carving on a stone or gem (as opposed to cameo) [syn: {intaglio}]