tracery

n. ornament, embellishment

Tracery is a series of intersecting ribs used in Gothic architecture, especially windows and, in the Perpendicular style of Gothic, vaulting. When used in windows, it is usually supported by carved vertical shafts. However, it is also used in circular rose windows, where there are no supporting shafts, unless they form a separate window underneath. Unusually, though, Lichfield Cathedral's nave clerestory has rose windows which take the form of triangles with curved sides.
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Noun
1. decoration consisting of an open pattern of interlacing ribs
(hypernym) decoration, ornament, ornamentation
(hyponym) fan tracery

(n.)
The decorative head of a Gothic window.
  

(n.)
Ornamental work with rambled lines.
  

(n.)
A similar decoration in some styles of vaulting, the ribs of the vault giving off the minor bars of which the tracery is composed.
  

Synonyms and related words:
arabesque, arc, basketry, basketwork, bow, cancellation, catacaustic, catenary, caustic, circle, conchoid, crook, cross-hatching, crossing-out, curl, curve, diacaustic, ellipse, festoon, filigree, fret, fretwork, grate, grating, grid, gridiron, grille, grillwork, hachure, hatching, hook, hyperbola, interlacement, intertexture, intertwinement, lace, lacery, lacework, lacing, lattice, latticework, lituus, mesh, meshes, meshwork, net, netting, network, parabola, plexure, plexus, raddle, reticle, reticulation, reticule, reticulum, riddle, screen, screening, sieve, sinus, texture, tissue, trellis, trelliswork, wattle, weave, weaving, web, webbing, webwork, weft, wicker, wickerwork