about that life

If someone says they're 'not about that life' it means that they don't or won't do something relating to that subject. It can be used in a variety of contexts and can be about a lot of things but it mostly used to reject someone inviting you to do something because you don't agree with it/don't like what they're doing/just don't want to. It can also be edited to fit the purpose more by adding in a word before the word life to describe what kind of life said person is not about.