Rita Risser’s response:
The word insubordinate can be seen as in = not, subordinate = subject to the authority of another. Someone who is insubordinate is refusing to recognize the authority of the employer. In essence, they are quitting because they no longer are willing to work for you.
Insubordination, thus, is always grounds for immediate termination, unless the order being refused is illegal, immoral or unethical. It is permissible to fire an employee for refusing to complete a task the employee deems trivial or unimportant.
Information here is correct at the time it is posted. Case decisions cited here may be reversed. Please do not rely on this information without consulting an attorney first.