In the context of alcoholism...
...I'd call a loser somebody who has given up trying to find and engage in recovery whether they are an alcoholic like my wife, or a codependent, controlling enabler like me. And even then I don't mean it in the pejorative. It's simply an accurate description of who they have become.
To me, everybody who has not given up the fight, regardless of the success they have or have had finding and maintaining sobriety, is not a loser. In this fight I believe you haven't lost until you give up. What I admire the most about my wife is that she has never given up. Ever. I love that.
Let me be clear that I believe the first step in both AA and Al-Anon is to accept that you have lost the war against alcohol or addiction. If that's what a loser is than I'm one too.
It is accepting this loss that opens you up to recovery, and by being open to recovery you, as far as I'm concerned, start to become a winner.
Take what you want and leave the rest.
Cyranoak