no life

Somebody with no life is one that doesn't value their own time, and so will spend it in ways that even they feel or know are a waste of their time (although they may not admit it). As different people enjoy different things and priorities vary by person, this is often used (by people who disagree with what is or isn't a good use of time) to judge and insult people who are actually happy with the way they spend their time. Alternatively, it could refer to somebody who is very dedicated to something (especially something frivolous or negative), at the cost of most anything else.