moody and unwilling to speak to people
sullen - glum
A person described as being ‘sullen’ is considered to be bad-tempered and unwilling to engage with or be pleasant to others. It can be as a result of a perceived slight, being in a bad mood, or feeling hard done by, but also due to a character flaw. The word has only negative connotations.
My class is made up of difficult teenagers. Instead of engaging, they typically just remain sullen and indifferent.
Brian always seems to be in a bad mood and it’s hard to ever get more than a few words out of him. His sullenness makes him very difficult to work with.
After I scolded my son, he marched off sullenly and locked himself in his room.