Dreaming about the letter O stands for openness and allows someone to show their thoughts without any truth being obfuscated or mislabeled.
It can represent freedom, breaking away from tradition, community activism and social change. The letter O can also represent a voice and individuality within society, as well as unity with friends and family.
The letter O can also represent some sort of transformation, either personal or physical. For example, it could represent the change from being single to being married, or from being healthy to sick. The letter O is also symbolic of infinity indicating that things may never go back to what they were before and will be more complicated for the individual.