refractory

adj. 难驾驭的，（病）难治的

reflective, reflectively, reflectivity, reflector, reflex, reflex angle, reflex camera, reflexion, reflexive, refloat, refocus, reforest, reform, reformation, reformatory, reformed, reformer, reformulate, refract, refraction, refrain, refrain from, refresh, refresher course, refreshing, refreshment, refrigerant, refrigerate, refrigeration, refrigerator, refuel, refuge, refugee, refulgence, refulgent, refund, refundable, refurbish, refusal, refuse,