The term is used to describe someone who has quit drinking/drugging yet still haven't made any changes or are still engaging in risky behavior (substitute addictions), or more simply are sober and haven't found god or happyness.
There is some truth to this, I have seen people quit, then do crazy things like quit their bipolar meds and drink coffee all day, some people become sex addicts, some people stay in the basement and play video games all day , etc.