Cách sử dụng
The expression "a fly on the wall" means imagining that you are invisibly present in a situation where you can observe everything that is happening without anyone noticing you. It is often used when talking about wanting to secretly witness a conversation or event without being noticed. For example, "I wish I could be a fly on the wall during the big business meeting tomorrow." or "I would love to be a fly on the wall when the celebrities arrive at the party tonight."