What exactly is "suicide by alcohol poisoning"?

Of course it is. But in practice, I think only about 2,000 people die of overdose on alcohol alone per year, which is about as many opioid deaths combined with alcohol–IOW, not counting benzos, etc… So yes, obviously it is very possible to drink a lethal amount of alcohol all at once, if that is what a person really wants to do. I was referring to inadvertent deaths. And yes, how alcohol–alone–really kills is by all the other associated behavior (e.g., driving), or just the long-term destruction of so many of the body’s critical organs.