Good question, gneiss. I look at it this way. I've heard there are lapses and relapses. A lapse is a small thing. A relapse is a bigger thing.
As I define it though, and this is just for me, there is no such thing as a relapse. When I choose to drink it is not a slip, a lapse or a relapse. It is a conscious choice to drink. Now I know most people won't agree with me, but only I make the choice to lift the drink to my mouth. There is no oops! about it. It's my choice.
I guess this is why I use the word addiction rather than alcoholism. I don't buy into the disease concept anymore than I think the addiction of smoking is a disease. Now, both will cause disease to be sure. Well, this is just the way I view things. To me, it's about accountability and having some degree of power over what I do.