Refractory (adjective)

1. Resistant or impervious to treatment, modification or change.
2. Not easily managed or controlled.
3. Not readily yielding to treatment or analysis.
4. Having a high melting point and resistant to heat and chemical change.

Origin:

Derived from the latin verb 'fractus' meaning 'broken', the word has been in use since the 17th century.

Examples:

1. The refractory material was used in the construction of the high-temperature furnace.
2. The refractory patient refused to take the prescribed medication and follow the doctor's orders.
3. The refractory metal was used to make the high-performance engine components.
4. The refractory soil was difficult to cultivate and required special techniques.
5. The refractory nature of the disease made it difficult to find an effective cure.