When you don't follow the rules — especially when they come from a teacher, parent, boss or other authority figure — you disobey.
A first-grader disobeys his teacher when he can't help running in the halls of the school, and a dog will disobey your shouted commands if you haven't trained her very well. When you obey someone's rules, you follow them strictly. The verb disobey combines the Latin obedire, "serve, pay attention to, or listen," with dis, which here means "not." The original Latin version of disobey, inobedire, used in rather than dis.