The type of mentality and behavior exhibited by someone, usually a male, who has been locked up for most of their life. Such an individual will act like a bully and try to intimidate others in situations where it is completely unnecessary and or unwarranted. This is due to the aggressive and cutthroat predatory nature of prison life. They are always quick to fight others for no reason. A cat with prison mentality will always call out another man who he thinks is weak and call him a "bitch".
"I hate working with that nigga George. He makes this job feel like lock-up instead of a legit nine-to-five. But you can tell he spent most of his pathetic life in prison. Look at all his tats and he only has one eye. I hate these faggots with that prison mentality. Leave that shit behind the walls".