What is the meaning of refractory?

noun

• Lining consisting of material with a high melting point; used to line the inside walls of a furnace.
  • synonyms: furnace lining

adjective

• Not responding to treatment.
  • usage: "a stubborn infection"; "a refractory case of acne"; "stubborn rust stains"
  • synonyms: stubborn
• Temporarily unresponsive or not fully responsive to nervous or sexual stimuli.
  • usage: "the refractory period of a muscle fiber"
• Stubbornly resistant to authority or control.
  • usage: "a fractious animal that would not submit to the harness"; "a refractory child"
  • synonyms: fractious, recalcitrant