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.

To make a poor stroke while rowing, perhaps by missing the water entirely. The boat jerked as I caught a crab with my oar.