Generally speaking, dreaming of loneliness means that the dreamer's environment is very bad and you keep looking for freedom.

Dreaming that you are lonely means you want to express your emotions.

Married people dream of loneliness, which suggests that the couple are incompatible and may be divorced.

A traveler dreams of loneliness, which means that you actually have a fear of separation.

Students dream of loneliness, which implies that you cannot be favored by others, and they feel very uncomfortable.