What does the "tight-lipped" mean? In what circumstances could I use it?

Native speaker’s answer
Rebecca
The "tight-lipped" mentioned in this video means to have one's lips tightly closed, out of a reluctance to speak. It's often used to describe people who will not share other people's secrets, who are considered to be reliable. Ex: I only tell secrets to people who are tight-lipped. Ex: I thought he was tight-lipped, but he shared my secrets with everyone.