1. 中年的
If you describe someone as middle-aged, you mean that they are neither young nor old. People between the ages of 40 and 60 are usually considered to be middle-aged.

2. 具有中年人特点的;保守的;过时的
If you describe someone's activities or interests as middle-aged, you are critical of them because you think they are typical of a middle-aged person, for example by being conventional or old-fashioned.

1. being roughly between 45 and 65 years old