A negative, selfish mentality characterized by a preference for others not to get ahead of or do better than oneself. It alludes to a phenomenon of a group of crabs in a pot, in which an escaping crab is pulled back down by the others so that none escape in the end. She dreamt of going to college and beginning a better life, but her parents' and friends' crab mentality constantly discouraged her from leaving the sordid life in which they were entrenched.

The belief that one is constantly under attack and must protect oneself from hostility. Don't be surprised if Ned reacts to you with anger—he has a siege mentality that makes it difficult for him to see anything positively. Many people living in that war-torn country have developed a siege mentality.