insubordinate
Refusing to obey someone who has authority over you.
Insubordinate means refusing to follow orders or instructions from someone in authority. When a soldier disobeys a direct command from their commanding officer, that's insubordinate behavior. When an employee repeatedly ignores reasonable requests from their boss, they're being insubordinate.
The word specifically applies to situations where there's a clear chain of command: military units, workplaces, schools, or any organization where some people have authority over others. A student who refuses to follow a teacher's classroom rules is acting in an insubordinate way.
Insubordination is different from simply disagreeing with someone or asking questions. You can respectfully disagree with a coach's strategy or ask a teacher why a rule exists without being insubordinate. What makes something insubordinate is the defiant refusal to follow legitimate instructions, often with an attitude of disrespect.
In serious contexts like the military, insubordination can lead to severe consequences because following orders might be a matter of life and death. In a workplace or school, being habitually insubordinate usually results in being fired or suspended. Organizations need people to follow reasonable instructions from their leaders, even when they don't always agree with every decision.