When someone is uncertain about something, they may use various phrases to express their doubt. A few synonyms for "be in doubt" include "be unsure," "be hesitant," or "be indecisive." Individuals may also use phrases such as "question the validity," "wonder about," or "have reservations." When expressing uncertainty in a less formal setting, people may use colloquialisms like "not have a clue," "be iffy," or "be wishy-washy." It's important to consider the context in which these phrases are used and to ensure that the meaning is clear to the listener or reader. Exploring different ways to communicate doubt can enhance one's communication skills and build clarity in expression.