squinch

squinch in architecture, a piece of construction used for filling in the upper angles of a square room so as to form a proper base to receive an octagonal or spherical dome. It was the primitive solution of this problem, the perfected one being eventually provided by the pendentive. Squinches may be formed by masonry built out from the angle in corbeled courses, by filling the corner with a vise placed diagonally, or by building an arch or a number of corbeled arches diagonally across the corner. In Islamic architecture, especially in Persia, where it may have been invented, the squinch took the form of a succession of corbeled stalactites. It was also commonly used in the early churches of Europe and the East.

squinch (archit.) †stone cut for a scuncheon XV; support constructed across an angle XIX. Shortening of SCUNCHEON
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squinch¹ / skwinch/ • n. a straight or arched structure across an interior angle of a square tower to carry a superstructure such as a dome. squinch² • v. [tr.] tense up the muscles of (one's eyes or face): Gina squinched her face up. ∎  [intr.] (of a person's eyes) narrow so as to be almost closed, typically in reaction to strong light: he flicked on the light, which made my eyes squinch up. ∎  [intr.] crouch down in order to make oneself seem smaller or to occupy less space: I squinched down under the sheet.