Is it farther or further?
"stubborn, obstinate, perverse," 1610s (earlier refractorious, 1550s, refractary, c.1600), from Latin refractarius "obstinate, stubborn," from past participle stem of refringere (see refraction). Related: Refractorily; refractoriness.
refractory re·frac·to·ry (rĭ-frāk'tə-rē)
Resistant to treatment, as a disease.
Unresponsive to stimuli, as a muscle or nerve fiber.
any material that has an unusually high melting point and that maintains its structural properties at very high temperatures. Composed principally of ceramics, refractories are employed in great quantities in the metallurgical, glassmaking, and ceramics industries, where they are formed into a variety of shapes to line the interiors of furnaces, kilns, and other devices that process materials at high temperatures.