The Collaborative International Dictionary of English v.0.48:

Triglyph \Tri"glyph\, n. [L. triglyphus, Gr. ?; ? (see Tri-) +
   ? to carve: cf. F. triglyphe.] (Arch.)
   An ornament in the frieze of the Doric order, repeated at
   equal intervals. Each triglyph consists of a rectangular
   tablet, slightly projecting, and divided nearly to the top by
   two parallel and perpendicular gutters, or channels, called
   glyphs, into three parts, or spaces, called femora. A half
   channel, or glyph, is also cut upon each of the perpendicular
   edges of the tablet. See Illust. of Entablature.
   [1913 Webster] Triglyphic