I often talk about unprofessional behavior of my boss and his lack of interest in his job to my colleague who is also an employee of my boss. Is that backbiting about my boss?
If you boss is a Mo'min, you must avoid criticising him unless he is doing obvious injustice on you and you will be then not allowed to talk about anything away from your suffering from his injustice. You should not mention any other thing about him which not part of your suffering.
Wassalam.