TRACERY
tracery
(noun) decoration consisting of an open pattern of interlacing ribs
Source: WordNet® 3.1
Etymology
Noun
tracery (plural traceries)
(architecture) bars or ribs, usually of stone or wood, or other material, that subdivide an opening or stand in relief against a door or wall as an ornamental feature.
A delicate interlacing of lines reminiscent of the architectural ornament.
Source: Wiktionary
Tra"cery, n.; pl. Traceries ( (Arch.)
Definition: Ornamental work with rambled lines. Especially: --
(a) The decorative head of a Gothic window.
Note: Window tracery is of two sorts, plate tracery and bar tracery.
Plate tracery, common in Italy, consists of a series of ornamental
patterns cut through a flat plate of stone. Bar tracery is a
decorative pattern formed by the curves and intersections of the
molded bars of the mullions. Window tracery is imitated in many
decorative objects, as panels of wood or metal either pierced or in
relief. See also Stump tracery under Stump, and Fan tracery under
Fan.
(b) A similar decoration in some styles of vaulting, the ribs of the
vault giving off the minor bars of which the tracery is composed.
Source: Webster’s Unabridged Dictionary 1913 Edition