A teraphasic coil was a type of warp coil utilized by the Xyrillians in the early 22nd century.
In 2151, the Enterprise NX-01 encountered a cloaked Xyrillian starship using the ship's plasma exhaust to replenish their vessel's teraphasic coils, which were damaged. Commander Tucker assisted the Xyrillians in repairing the coils, only for them to break down six days later. (ENT: "Unexpected")