Quick answer
A Uninyvin cable is a specialised single-core flexible wire built for demanding, mission-critical wiring — with a heritage in aircraft applications. It pairs an annealed tinned-copper conductor with heat-resistant (105 °C) HR-PVC insulation, often with a glass-fibre braid, for high reliability where ordinary wire would fail.
It suits high-temperature and heavy-duty installations. See APAR's Tarang Shakti Uninyvin cable, part of the communication cables range.