recalcitrant

This term describes a stubborn refusal to comply, often carrying a sense of defiance or active resistance. When applied to people, it suggests a clash between an individual's will and an established authority, evoking an image of someone digging in their heels. It is more formal than stubborn and implies a specific conflict with rules or discipline.

In medical or technical contexts, the word shifts from a behavioral trait to a functional property. It describes a condition or a material that simply will not respond to standard interventions. This usage emphasizes the failure of a process rather than a conscious choice to be difficult.