[harleyquinn]

Well, in the terms of someone with an alcohol or drug abuse, and enabler is someone who, rather than help the person get better in terms of knowing not to give them what they "crave" and admitting that they have a problem does things like a) deny there is a problem, b) ignore it and hope it'll go away, c) may make excuses for the person's behavoir.
Basically, denying that there's a problem does not help the person get any better. I know that someone can't get help until they want it for themselves, but people that are enablers make it hard for those people to get better even though they may think they are doing nothing wrong since they're not giving those people their drug of choice directly. Maybe someone else has a better definintion, though.