Definition of periphractic in US English:



  • Designating a region of space having one or more internal bounding surfaces (or curves, when the region is two-dimensional) unconnected with the external boundary (e.g. a globe with an internal cavity, or an annulus), so that a closed surface (or curve, when the region is two-dimensional) may be drawn within the region which cannot be contracted to a point without passing out of the region.


Late 19th century; earliest use found in James Clerk Maxwell (1831–1879), physicist. From German periphraktisch from Hellenistic Greek περίϕρακτος fenced round (recorded in (neuter) noun use, περίϕρακτον enclosure; from ancient Greek περι- + Hellenistic Greek ϕρακτός fenced, protected (from the stem of ancient Greek ϕράσσειν (Attic ϕράττειν) to fence in + -τός, suffix forming verbal adjectives), after περιϕράσσειν to fence, fortify all round) + German -isch; see -ic.