This expression is a funny way of saying that someone is old. To be over the hill means that someone is old, and so not able to do things that they used to do. You might see this expression on birthday cards or hear it in movies. This expression is usually used in a joking way. We also look at the expressions to be no spring chicken and long in the tooth. In a more positive way we also look at the golden years or the golden age. Getting older can have a lot of benefits too!