Here are some signs that your boss might be a bully:
1. Your boss is in your head - You find yourself carefully planning anything you might say in front of your boss, you self-censor and don't feel you can be yourself.
2. Public criticism – your boss points out your mistakes, or criticises your performance in front of other people.
3. Favourites and outsiders – your boss seems to have an inner circle and you are not included. Maybe they have insider jokes. Perhaps you often don't get the information or resources other people on the team are getting.
4. You have or are tempted to call in sick just to avoid dealing with your boss – just the thought of going to work makes you feel stressed and sick.
5. Your job description and workload change a lot – you have way too much work, or not enough, or your responsibilities are changed frequently, maybe your job description is unclear, and you can't really be sure if you are performing well, because it's not that clear what you are supposed to be doing. This can be subtle, because of course priorities do change, but your boss might be using this instability in your work to make it almost impossible for you to show that you are doing a good job. Check if it's the same for everyone in a similar role to make sure you are not being singled out.
6. Weird timing – your boss makes contact to check if you've done something or give you something new to do, of course this is what managers do, but your boss often does this at 4:55 on a Friday afternoon, or by calling you 20 minutes before you are due to get to work.
7. Anger or ridicule in response to your feedback – If you politely point out to your boss that he/she has done some of the above and that you'd appreciate if he/she stopped, and your boss laughs at you, or gets mad, you've probably got a bully on your hands. Or at least a rubbish manager.
Take some action, and do it right away!