Someone who's maladjusted has a hard time coping with life's challenges and difficulties. If you're maladjusted at school, you just can't seem to fit in with your fellow students or figure out what your teachers expect from you.
Maladjusted people can't deal with fairly ordinary stresses and trials, or they can't get along with other people. You might feel socially maladjusted if you move to a new country that's culturally very different from your home, for example. Sometimes this adjective is used to describe a system, like the economy, to emphasize how unstable it is: "This maladjusted economy is creating a society of haves and have-nots."