1. avoid making a decision or expressing your true opinion about something
give your true opinion instead of sitting on the fence
The idiom 'to sit on the fence' means to avoid making a decision or taking any action. When you 'sit on the fence' you are essentially doing nothing and are not on one side or the other of a decision or disagreement. This phrase is often used to encourage someone to make a decision or to take action 'you can't just sit on the fence on this issue', you need to make a decision.