Answer: refractory

AnswerCrossword Clue
refractory(of a substance) Resistant to heat; hard to melt or fuse
refractoryStubborn or unmanageable
refractory(of a person or animal) Resistant to infection
refractory(of a person, illness, or diseased tissue) Not yielding to treatment
refractoryResistant to a process or stimulus
refractoryunruly, stubborn / a stubborn person