The straightforward dictionary definition is “Defiance of authority; refusal to obey orders.” The workplace, however, generally isn’t set up where managers expect perfect adherence to management direction. Often, professional-level employees are given a lot of leeway in how they approach their job. Good managers recognize that their direct reports are the experts in their jobs, and rely on the employee to push back.
The difference between insubordination and pushback generally occurs in how the employee approaches the situation. If an employee ignores manager instruction and does something else, that’s insubordination. However, if the employee contacts the manager and explains why the manager’s guidelines are a bad idea, a discussion ensues, and they ultimately agree, that’s pushback.
Sometimes insubordination is protected by law. For instance, there is a legal doctrine called “wrongful termination in violation of public policy in the United States.” An employee can be protected when refusing to carry out an illegal order. While it is insubordination, the courts will side with the employee. Whistleblower protection is also widespread.