If something is repressed, it's restrained or held in. You may be full of repressed anger toward your brother over that terrifying incident from 4 years ago involving the frog and your hooded sweatshirt.
The adjective repressed often describes emotions or desires, especially those that could be considered shameful or distressing. When an emotion is repressed, you hold it inside so you don’t have to show how you feel. Sometimes you aren’t consciously aware that you're doing it. You might not even realize that you have a repressed longing for that cute guy in math class. A person who has many of these pent-up feeling is said to be repressed.