When someone says they are on the fence, it means they are undecided or unsure about something. Some synonyms for this expression include sitting on the fence, straddling the fence, hedging one's bets, undecided, uncertain, ambivalent, equivocal, hesitant, doubtful, and wavering. Sitting on the fence implies a sense of being stuck in between two options, unable to make a decision. Straddling the fence is similar to sitting on the fence - it means being unsure about something and not committing to a definite course of action. Hedging one's bets is often used in the context of gambling and refers to betting on both outcomes to minimize the risk of losing. Overall, these synonyms convey varying degrees of uncertainty and indecision.