My definition of enabling is when I deny someone the consequences of their behavior.
It's tricky territory, for sure. Lots of gray area.
For alkies, it means I do not cover-up for them, lie to them, or lie for them in terms of their drinking.
For example, a friend's mother had asked me to write a letter to the judge and I agreed because my friend was sober. A week later, same friend walks into my store smashed. She wanted the letter to give to the judge. I refused, of course. Then I called her mother and explained that I was no longer willing to write the letter because her daughter showed up at my store drunk.
Another time I picked up a girl from her mom's house and brought her over to my place. She was smashed on pills. It was a little hard to see at first but then it became glaringly obvious when she couldn't even make a pot of coffee. I put the girl back in my car, drove her home, and asked to speak to her mother. I told her mother the reason I was bringing her home was because she was intoxicated. Today she is one of my best friends.